So you too need to develop some reserve accounts - one for repairs, and also one for property taxes and property insurance payments - which are big expenses that are due once a year, but your seller will likely not collect like a bank might escrow for you.Know that seller financing gives you lots of options to negotiate your deal - but that cuts both ways.  

Converting the sunroom into a bedroom would cost 4k-5k. 

First, all first flips take 2-3x as long as you think and cost 2-3x as much as you think.

The average single-family home may cost $10,000 and that's a new install.

If you are planning on buying it with a smaller down payment, that will also increase your mortgage costs as you are borrowing more and also need mortgage insurance.The price of the home (from the seller's perspective) is based on market value and condition, not on whether or not it matches the 1% rule.   

One of my properties cost me a little more, but the other two were less than what I was paying with foremost insurance.

Tenant’s failure to maintain any item for which Tenant is responsible shall give Landlord the right to hire someone to perform such maintenance and charge Tenant to cover the cost of such maintenancePremises defined in the lease as follows:  Landlord rents to Tenant and Tenant rents from Landlord, the real property and improvements described as: address of the rental property (“Premises”).1.

I don't know any private lenders and hard money makes me nervous since I'm a buy and hold guy and the payback isn't as cut and dry as it is on a fix and flip.

Unless your mechanically handy your maintenance costs will eat you up.  

We currently own one door (split acquisition and closing costs and contribute equally to management and ownership), and have split equity and cash flows from the property - also pretty standard in my experience.My question is this - I want to purchase a house hack and would like to use our current business entity for accounting purposes (tracking income / expenses / etc).