This company designed our new kitchen after we gutted the old one, sold us the cabinets, counters, plus a bath vanity and sink, and had another contractor install them.

Well, if you don’t have a Lender Approved Contractor under contract for a price that falls within the appraisal, and they filled out the proper lender forms, you will Not be approved for the loan.....end of story.  

The roof was brand new installed in January 2018 and had no issue during the hurricane season.

Make sure you have the tenants sign the proper legal documents turning over possession of the unit to you and that they hand you the keys before you give them the cash! 

They were not prepped and painted properly by the previous owner and they look awful.

Make sure to install a good vapor barrier, and have proper ventilation and you should be ok.

IF they don't, they force you to make conservative assumptions (e.g. expenses, capex, vacancy, etc.) and you end up putting in a lower offer.Another tactic / strategy is to simply give him his price (with the proper out clauses), get the information and then re-negotiate the price.

If your goal is to generate passive returns, real estate (done properly) may not be the right vehicle. 

He charged me $2k to purchase and install a 75 gal gas water heater, and dispose of the old.

I got quotes from 4-6k to install central air.