I don't think you will make much money turning pro, being realistic.

Since your last competitive fight was 4 years ago and you had stamina issues, I would not rush into a professional fight.
I would at least test the waters first with a couple of Amateur fights, to see how comfortable you are at that level.

A trainer losing a few fights would not be a turn-off a boxer.
A few bad knock outs, or the trainer needing to take the fights for the money would have me running away.
This would have more chance of happening in the pro's.

Take a couple of Amateur fights, see how you feel before you turn pro.
You might find more competitive fights, experienced fighters in the amateurs so I would not rule it out because it is amateur boxing.