Seller financing is an equity based loan, look to the UCC as to default of installment contracts, they become void, points or loan fees are not charged on equity financing.......I said not charged when I should say, should not be charged as I'd bet sellers are not in compliance, they can just lose their note and suffer any consequence that goes with unlawful lending.

Is there a rule of thumb i should be using like 10% for a traditional management fee? 

ARV – Desired Profit – Closing Costs to Buy – Repairs – 10% of Repairs – Holdings Costs – Concessions – Realtor Fees – Closing Costs to Sell = Your Offer (MAO or Maximum Allowable Offer).ARV: After repaired value or what you think it will sell for once repaired.Desired Profit: This should be taken off the top first.

There are hidden costs in all strategies in real estate.

So 3 to 4 months of no rent and $400 to $500 in eviction fees later, they had to pay someone to clean out the house at about $500.  

I pay them a monthly fee and a listing fee so they stay out of my business.

The price sounds really tight, in case the rehab costs are more and then hard money loans, points, fees and closing costs when selling.  

If tenant rep they generally split 3%,3% although it is whatever you negotiate as an owner for fees.

It's up to you, but I think the pet deposit and fee make up for any damages and it provides an advantage marketing your rentals. 

HELOC can free up the additional 10-15%, but comes with a price (fees, higher rate, higher risk).It may take a while to save another down payment on annual positive cash flow from 1 property, depending on your numbers.