For example there is a big set back from the wetland boundary line that eats into your buildable area.

I am being conservative with my numbers so it is eating a lot of my cash flow.

@Nicho PruettIf they didnt flush it just replace the toilet if the did get a gallon or 2 of muriatic acid will eat through the concrete then flush with water no worries

Try to figure out average utility cost total for last 3 years from current owner and try to get a credit held in reserve so post closing you do not have the ongoing utilities cost eating so much into potential cash flow while you work on a long term solution.

The deal is going to be too small to eat the legal costs.

They may be over charging for maintenance and other items which will obviously eat into your bottom line. 

Good chance you’ll get stuck not being able to sell and holding costs will eat away all your profit and then some.

From what I've read in David Greene's "Long Distance Real Estate Investing", some property managers may charge a fee for every new tenant (like half of first months rent) and this would eat into my cash flow.

Things like closing costs to buy, closing costs to sell, agent commission to sell, seller closing help for the buyer, financing costs, carrying costs etc can eat up a lot of the gross profit on a deal.

Tenants know when they are getting a phenomenal deal  and often (in my experience) will just eat the increase because they know there's nowhere else to go as cheap.