So besides penciling income/expenses and profit/loss, I would also be looking for comparable sales to justify your purchase price. 

rental properties can be expensive. 

--What is your average closing timeframe?

(source)It also states this:  The following requirements must be met by taxpayers or RPEs to qualify for this safe harbor:*Separate books and records are maintained to reflect income and expenses for each rental real estate enterprise.

The cost of money would be considered an expense.

However, you can deduct any expenses you have while at your destination that are directly related to your business."

In my market the very cheapest possible whole-house project would be $250ft2, medium-grade would $400ft2 and most are $800-1,000ft2 (average home price is over $1M so we're talking luxury finishes).

All of my LLCs have their own bank accounts, books, expenses, etc.But what else do i need to separate? 

Reality is that repurposing a tin can into living space is expensive.

My average monthly cost for everything is about $350.00.