I learned to call others investors who referred me to trustworthy contractors.

If you’re aiming to attract higher-paying renters, consider going taller (10-12 ft) for flexibility with larger items or small vehicles—this may boost interest and rental rates.

i wasn't in a position to buy it by then so i referred them to a friend of mine and he bought it. 

These are just a few basic things I'd look for.In reference to the agent, you definitely want to find the investor focused agents that does a lot of deals and lean on them for their expertise.

While you can't create limitations against their lease and legal rights they have for quiet enjoyment, things like keeping common areas free of clutter or routine maintenance items that are tenant responsibility can often be added to help keep the expectations on both parties clear.

I was just referring people to them which has stopped. 

Wondering how to build trust in him to do seller financing with us after this.For reference we have 100% close rate, my thoughts approaching this is to counter back and say the risk of default is very rare, if he's worried about the park defaulting he just needs to save up $20k in reserves and he'll get paid $70k in income for the park for the next 5 years while he waits for balloon.

I'm looking to add some resources to my list, agents that have done flips and vetted general contractors that have references!

If $23k is just a “hope and a prayer” then he’s going to have a very hard time producing any CREDIBLE itemized bill.  

I do my own due diligence and call all reference numbers, past landlords, and do an in person interview.