Don't apologize, don't explain how the 'chosen' tenant was more qualified than they were, wish them well in their search.You're running a business and you've made a business decision. 

Having the seller carry a second is not a problem for the first, as long as their business with you is finished and the loan has closed.

It's a business - acquiring/building, managing, and growing a business. 

Call the zoning department again, and this time ask specific questions: Is a variance required, or can you proceed as-is?

I have found enough business and made enough money not to need to expand outside of this market.Section 8 is a whole different ball game but I find the program is unique in that it's a 3-party relationship adding the variable of a government agency.

Quote from @Matthew Cook: Dig into those comps with a realtor doing business in that market.

I dont know your business model exactly but I assume you collect some referral fee from the supplier?

I think you just have to work it in as the cost of doing business. 

PMs are busy - if you email a PM and say "Hey PM, I'm looking at 123 Main St. and I think it will rent for $1500 a month, does that sounds right?"

Scotia Bank in Costa Rica will allow you to open up an larger account as 'business owner' if you own your properties in an LLC but the process of opening an account is much more difficult.