I, too, was looking at starting a GA finance business on the side. There are a few issues that make it more difficult - not least where about 10 years ago, an aircraft was thought to hold its value well, but now they are seen as depreciating assets (just look at twins). Permit and plastic aircraft tend to do better, but it can take an eternity to shift some and not many underwriters want aircraft on their books instead of cash - which is why the minimum lend and deposits have increased.
Agree with Sam, Mono and Baikonour: better to use cash (business usage excepted).. And Sam is right - used will be better and keep cash to keep it in the air. I know someone who purchased a new model of what I have a share of and surprisingly, his operating costs were not much different to ours. Factor in the depreciation and he is shelling out a shedload for the same aircraft, same reliability, same performance, same comfort. It was shinier, the seats smelt new and he had better avionics (not by much, though).
I have been thinking of offering an operating lease type arrangement (lessee only has to add fuel and possibly insurance) on second hand planes, but it is very risky..