Loan Shark? The fat cat
Be a merchant 'o' money, beat the banks at their own game, and beat up those people who fail to pay on time. If you want an excuse to play it rough, send the boyz round, and still have time for tea with the mayor, then this could be your niche.
Once you have an amount of cash lying around waiting for some investment project, become a people person and invest it in people struggling to get ahead. Help them to struggle! Every city needs one, you can justifiably make cash without caring for morals as cities always have stacks of poor people struggling to make ends meet. Find out what the banks are offering and undercut them. If the banks are offering around 5% interest on loans per year - go in at 4% as a starting loan rate, you can always increase it later. If you structure the loan repayments such that the first to be repaid is the interest and only when that is all paid off do they actually repay the loan itself then if they default early they still have all, or most off, the actual loan to repay. Confused? Well, play around with some numbers and if it still does not make sense then maybe you should consider drugs, 'security services' or 'escort services' as your line in thuggery.
Typical loans you can arrange include those to buy a shop, for stock to start a business, or as a mortgage for properties. And if they already have a loan or two, and maybe have a lot run up on their credit cards then it is time for you to step in with that consolidation loan where you pay off their loans now and they have a loan to pay you back.
So, what if they stop paying? Well, the other part of a loan is the collateral. Now, that is a good word to include in your spiel. Basically, if they fail to make a repayment then you need a way to get the cash back, legally or otherwise. Collateral could be the deeds to their property, or a clause in the contract forcing them to sell something to raise money to pay you (maybe their whole business). An unwritten clause may (fail to) mention broken limbs.
For success, you need to understand when you should be legal and when illegal, and to remember that one person's illegality is another's immorality. The former is punishable in this life, the latter in whatever follows. Miss one payment, did you; sorry but now you have to repay everything. Can't do that? Well take out this consolidating loan! Only 13% over 300 months.