So I am in the process of purchasing an reo double wide on 3 acres and am trying to figure out specifically what documents I should get to review before we close in 2 weeks.

It sustainable product, has natural anti-bacterial properties (one of the reasons its used widely in hospital, care home, and daycare settings), and does not off-gas - or release in a fire - dioxins and other toxins PVC will produce. 

Is there a number or percentage that's typically used as a placeholder for vacancy, maintenance & capital expenses when running numbers–is there an industry-wide standard?

Older than 1995 or so single wide 3/2 I'd offer $5k or so.  

I'm a practicing CPA in Houston but have a pretty wide business network. 

In the area that I am looking, the lots are 30ft wide, which makes it very difficult to provide off street parking (so on street parking is typical for the area) for anything but single family houses.We have identified two lots next to each other and are currently pursuing purchasing them.  

There are actually more than 100 different real estate crowdfunding companies that offer investing, so I think the biggest problem for a new investor is weeding through them. 99% of them claim that their investments are the best, but actual quality varies widely.

But the range can be pretty wide.

It seems to me that they'd be helpful in obtaining even a foundation for the wide breadth of knowledge that is the RE investment world. 

If you're really having problems finding a lender that knows this, it may simply be because Georgia doesn't have a particularly large immigrant population (I'm in CA, so this is normal for us - everything from Italians to Koreans to Mexicans).If you are in the country unlawfully but have an ITIN, you will need to search far and wide for an "ITIN Mortgage Lender."