Debt in a Game example

I borrow money to buy a Desktop, a Car, a home. Interestingly, I took on a Debt disadvantage forcing to have less disposable income but in return I have an Asset.... but where is the Asset I took debt for? Should a character take a disad to get a Car, a House, or money for his adventuring Start-up capital?

Assets = Equity and Liabilities; Duties

The Debt disadvantage resulting to a House that is not 100% yours is already in some kind of game balance IMO. The uncertainty makes opens the door to the risks everyone naturally faces when borrowing a large amount of money, that anything happening to that asset can destroy your future.
If you know any business owner who borrowed to start his business (who makes an honest living) such an expensive asset is something to regularly lose sleep over and worry about.

Technically you have a duty disadvantage that is on call, and have a ton of consequences: loss of credit-worthiness, bad reputation, possibly jail time etc.. etc.. This makes for a Perfect Vehicle to design characters around. Everyone who joined in the venture can all have Debt and Duty. Working for someone and failing in the duty will has significant consequences, failing in a business you borrowed to build has more significant consequences.

In TL3, a status 0 farmer making $700 a month can sustain -10 cp of debt for $100/mo still make their cost of living, anything more requires a drop of Quality of Life and lifestyle (up to -20; which is -$200 forcing the farmer to live in 500/mo cost of living). The higher the TL the more you can't sustain a threshold of -10.

Debt has a broader meaning 

Don't limit debt as owing someone money, expand your thinking to that Cell-phone Plan you got, internet or utilities billing, the mortgage for house and car or Business, OR the Lock-in contract for your apartment where you have to pay X amount every month even if you want to terminate the contract you suffer negative consequences.

Almost everyone has some form of debt, by the broader definition. Everyone has a cell phone plan, a lock in period for their housing to bring down the cost, and various other financial exercises that can fall under debt. So its normal in the modern world to leverage future earnings into investments or conveniences or for a dignified existence.

Living within Means

So characters now have debt, and it can reflect their housing. So what happens to CoL. Now it reflects Utilities, Food, and lifestyle. 

To scrape up some cash the GM may require a Professional Roll or a combination of various Professional Rolls to find some time to make money. In real life, this is pretty much the Challenge and Adventuring many regular people get into: Deal Hunting, Cross Training, and various Odd Jobs.

Sadly in many situations work takes up 50 hours a week, with small breaks of incredible boredom during the 50 hours. The GM may want to ask a professional roll to slip some online work (trading online; making and working on apps or products to sell; part time work). Although I think this should be done at the end of the month with a skill roll, with the Job roll modifying your "2nd" job roll. 2nd sources of income is becoming a trend these days, and the 50 hour work week is slowly paying less per hour as well (all over the world).

Nothing is for Certain: Job Market; Consequences of Defaulting

In medieval times, a farmer makes a living as a farmer their whole short life. Social mobility was in several generations, in Modern times it i within one's lifetime. Debt has the ability to move one up the social ladder (investing in a business and growing that business) or Falling down the ladder (one can still be fairly valuable for their experience if anyone would hire him/her). 

In Modern Times, there is greater uncertainty and "friction" when it comes to the job market. the character's Job or means of living is more uncertain than their ability to pay their debt... except for countries which has subsidized training and education so that people simply retrain to fit a more long standing profession in the face of greater and greater automation. 

It can be annoying when a dressing part of the world comes to light when the GM is building worlds :( anyway, if the character cannot sustain his payments consequences are pretty bad. One simple consequence is living beyond your means is really just getting poorer. That -10 to wealth from Average is now Struggling, not just a loss of Income generation BUT a loss of assets. In gurps since Debt scales, a struggling person with -10 debt loses an amount proportional to their assets. 

Examples 

Osman and Thomas (Pregens in GURPS Modern Fantasy) both are Filthy Rich. In Haven their Starting Wealth is $20,000,000 and 2,600,000/monthly. Their debt, a number of infrastructure projects have a realization of 10 years making the total cost ($480 Million combined). Because of the synergy of the two business partners: Osman being a master empath and diplomat, and Thomas who is incredibly shrewd and skillful in business these two characters were able to start a very deviant business type: Shadow ISP (creating a unlisted and technically illegal ISP infrastructure). 

Basically the two characters sell Internet bandwidth, but they do it with many dummy accounts and hidden behind many false infrastructure project. Exploiting the City's convoluted Urban Sprawl and the many dizzying relationships with other local ISPs, Osman and Thomas are the guys you talk to if you want to have complete anonymity and electronic "commodity" trading investing and banking. Such a secure and Anonymous Marketplace is going to have a lot of  

Their wealth is divided into many shell assets warehouses, low-rise-buildings (being used as DR sites and collocation that participate in the electronic commodity market with idle processing) built around CBD area in various properties that have some legal and diplomatic immunity. They connect to the CBD area wirelessly through many dummy terminals. Speedy is the parkour programmer set up a very interesting array. The infrastructure they set up has been instrumental for black markets and shadow banking as well as sheltering human rights groups, all the flavors of activists, and some insurgents. Tedora also benefits from her relationships with two Partners and provides legal muscle    

Despite all this Osman and Thomas can only work with their $600,000/mo. CoL and what ever revenues Thomas can scrounge up for them with his business savy. Thomas with his "Hobbies" and  

The two characters reflect the main lessons of business: People Skills and Business Acumen. Note that Thomas is a bit of a computer wiz, and Osman is an "Old Money" elite as a Prince. They have Peiter and Speedy as their friends and retainers.

Currently there is a big debate where Emerging Market's Growth is coming from. Some say education, or increase of living standard, etc. My theory is that its a new *cough*sucker*cough* to take on debt and invest in infrastructure projects that should improve productivity and quality of life. lolz. I'm sure infra projects do, but never at the level promised. Its all a gamble really.

Thomas is an aberration of having the right amount of technical abilities in your home country. The funny thing about it is that, it takes a person like Osman to find the right people to do the project and Thomas and Speedy to implement the design, and Thomas and Osman to know who he has to pay to let such a project go through. Mama Mary and her crew also are very important.

I'm beginning to think I can write a whole TV series around these characters about doing business in the 3rd worlds. With the surrounding characters showing day in a life of struggling in such a place.