Most lenders will add back in depreciation and around 1/2 of your milage expenses.

Say they sold the properties over 3 year period and could not sell the rentals together as a portfolio.Could they put the money from each sale into a DST then use the total to buy a expensive rental property?

You have used home equity lines of credit to purchase investment rentals and want to know the best way to pay down the HELOCs.Between the two properties you bought, after expenses, you have $250 a month positive cashflow to use.What I like to do is pay down some principal every month with my positive cashflow.I use my extra active income from real estate commissions helping other investors to pay down the principal even more which just frees up that credit for me to use again.I know I can refinance the HELOC debt before it changes to principal and interest as it is just interest only payments as yours are.One difference is the cashflow, I have greater positive cashflow and could make the principal and interest payment in the future with the extra cashflow I already enjoy.I always get HELOCs on my income properties as well after purchasing them to pull out as much of my downpayment as possible.

Purchase price: $320,000 Currently have a long term renter, the rent pays the mortgage and other expenses but provides no cash flow.

3) Remaining $5625 is reimbursed to me as home office expense.

With your background in lease management and site selection, that could be a natural next step.Regarding STRs, I can understand the hesitation—accurate expense tracking is critical, and not having that data can make evaluating deals frustrating.

Read Gary Keller's The Millionaire Real Estate Investor for a deep dive on expenses. 

I use it for expense tracking (which is great) and have been transitioning to rent collection/cash management.  

Cash on cash is only what you are receiving divided by your expenses.

@Eric Coats, to answer your specific questions, estimating expenses are pretty simple.