Also avoid prepaid contracts or flat rate.

The rest (Processing ,underwriting,Credit Report Fee,Tax service etc.)are almost the same.Total closing 3k+ without prepaids and initial escrow payment.

Most get paid on pre-paid debit cards but not very many pre-paid cards work with ACH debit for online rent pyments.

Interest paid monthly or pre-paid or paid at the re-sale?

In terms of taxes, insurance, prepaids, origination etc.  

(Your basis is the original purchase price, plus purchase expenses, plus the cost of capital improvements, minus any depreciation and minus any casualty losses or insurance payments.)Deductible closing costs include points or prepaid interest on your mortgage and your share of the prorated property taxes.Examples of selling costs include real estate broker's commissions, title insurance, legal fees, advertising costs, administrative costs, escrow fees, and inspection fees.If you have any additional costs that coincide with these costs include them in your overall numbers and it will help your reduce your total.

Home insurance premium is prepaid at closing, and insurance and taxes might be escrowed something like 3 months worth.I recommend you check out a prospective property's Zillow for tax info and monthly payment estimates, Google for things like U-haul and appraisal averages, and ask around or call for quotes on garbage pickup and the like.BiggerPockets has quite a few articles on guestimating Cap Ex, vacancy, property management, and more.

How would I work the numbers if there is still a balance of the prepaid rent?

Here are a few things I usually adjust for when underwriting off an OM, whether it be from LoopNet or not Closing Costs I can't tell you how many times I see CoC calculated on an OM using just 25% of the purchase price without regard for closing costs, prepaid insurance, prepaid taxes, or anything that might be required to closeVacancy % I bring this to the market average or if it’s a small to mid-sized building, I’ll look up and see how many units are being marketed online for rent.Property Management I will bring this to what the company I will use chargesStuff like that usually changes the numbers a bit.

There are a lot of other things but I won't make this post a novel, I'll just say keep in mind that since you'll be holding this property as a rental, all the money you put into the property extends your Break-Even point on recouping all of your prepaid money (land purchase, Soft and Hard construction cost, Loan cost from the construction loan) you're hoping to get back from tenants paying down your mortgage, basically when will you really start to make money on this deal?