Are you insane?

If you make 10% on each plane, and then have to eat a loss because of a bad
buy or something, it can wipe out a lot of other deals. Seriously, buy a
172 for 45. Spend 2 on it, and sell it for 53. Now, find out you need 10k
in repairs to get your money out of the fourth one - and it starts to look
lame. Now, try to make 15%, and listen to both sides squeel like pigs.

Also, Van Bortel distributes/sells a lot of new Cessna's, so he has
relationships with lots of FBO's and schools that way. Those relationships
multiply.

Add in the fact that you are now despised and mistrusted by most of the
population because you are now a salesman. You can look in the archives here
about how most folks think about brokers and sales people. If you want to
know real frustration, go try to buy a plane from someone who is NOT a sales
person. I have heard sales people tell a few whoppers, but plane owners
take the cake by far. Still, its the sales people that get hated.

If you are not sufficiently discouraged, then know that the world does not
need more brokers that are not full service. Have a maintenance crew and an
interior crew that can fix your planes before and AFTER you sell them.
Standing behind your planes with a warranty can't happen if you can't fix
them.

The only other thing I can think of is opening a consignment lot may be the
way to go. Start an FBO where the ramp and hangars are dirt cheap, and let
people put the planes there for sale for a fee.