We stay close to public transportation, particularly train stations.

Since it is an FHA, there probably will not be much they can do because the FHA mortgage is very particular on proper terms. 

Not sure about NY, but in PA, pet deposits are non-refundable to the tenant.

The worse thing you can do is force a non-paying tenant to remain in your property. 

My crazy idea is to cash out refinance the loan to a non-VA loan as soon as possible (ideally before living there for one year).

I’m not sure if this has been posted here before, but wanted to briefly share this information we found out regarding FHA. As a military member we have exceptions to the normal occupancy rule. Check it out:

“FHA loan...

He told his client, for an REO, don't bid more than 50%, or in this case $150K particularly if you're a cash buyer.

I'm not sure I understand the question, but as long as you give the current tenant the legally required length of notice for the non-renewal of the lease, after they move out, someone else can move in immediately.Edit: if it's clean and move-in ready

Would we ever be able to have personal use on non-rented weekends or stop after a couple of years to turn the RV into personal property?

To even consider before you start construction you would need an executed lease with a large non-refundable deposit upfront to show the tenant is serious and committed to the sight.If this tenant is not larger corporate but smaller individual or group there could be serious risk to building the project and then the tenant ends up falling out before taking occupancy.