I have a Bahamian rental (not technically the Caribbean) that is grossing six figures this year and we are still using it for about a month. 

•Do they have a formal trainning program and mentorship•Do they use a quality CRM•Do they have an experienced marketing team•What is the average annual gross commission for an agent in their office•Is there a specialist in the category of CRE I am interested in (Office, Retail, Industrial, Medical, etc) that can help me grow

Maint, cap ex, vacancy, etc....or is that just the gap between your mortgage and potential gross rent?

They will multiply the gross rents by a multiplier to estimate value.

The gross rental income in 2017 was $31000, which meant 4 of out 9 apartments were vacant.

Looked into some BLOC's but many want gross rental business income of $5-10K per month. 

The value for multi-unit properties revolves around gross annual income just like every other business. 

We did some renovations, painted, fixed items and it was looking cute and was ready to rent but things came up after in a series of unfortunate events-- like the call I got from the tenant about animals in the ceiling... so I hired a trapper I to get rid of the critters... and the call a month later about a gross smell coming from the back of the house... which turns out was a rotting squirrel family in the ceiling-- guess the trapper didn't quite get the critters out before plugging the hole where they were getting in. 

If you are going conventional mortgage, owner occupant (this would be for anything 4 units or less that you live in one of the units), your basic underwriting standards are up to 4x gross earnings and 20% down. 

The trick here is using the potential rental income from the duplex to increase your gross income so you could borrow larger amount of debt.