You can find some 2 units under or around $250K but they have been sitting on the market for over 150 days which tells you its not a great deal if it were an investor woud have already purchased it 4 month ago.  

I’m looking for some advice on a fix/flip property that I purchased with two friends almost two years ago.

My question is: After I build the units, can I do a cash-out refi and use the equity to purchase another home? 

Purchase price: $271,000 Cash invested: $30,000 Duplex with 1 bed, 1 bath in each unit + 3 car garage in a great neighborhood.

Recommend you first figure out the property Class you want to invest in, THEN figure out the corresponding location to invest in.Property Class will typically dictate the Class of tenant you get, which greatly IMPACTS rental income stability and property maintenance/damage by tenants.If you apply Class A assumptions to a Class B or C purchase, your expectations won’t be met and it may be a financial disaster.If you buy/renovate a property in Class D area to Class A standards, what quality of tenant will you get?

Too many newbies seem to think they can blindly follow "old" advice in today's real estate market and be successful.Many, basically get taken advantage of by those in the industry that have an incentive to keep newbies blind to new realties, just to keep their good times rolling.What many newbies have figured out is that they can't make the numbers work on rental purchases in their states - like California, Arizona, New York, New Jersey, Washington, etc.What they have NOT figured out is that if they go to cheaper markets, they aren't being shown Class A rentals to buy.

We purchased the house about 3 months ago and are owner financing it.

Purchase price: $275,000 Cash invested: $294,000 Sale price: $355,000 The property is a 2 bed 2 bath with a den and a 1 car garage.

Where the SBA 7A can be used for all parts of the purchase and is generally Prime+ 2%, 10 years, the 504 (bricks & mortar only) is generally Prime -2%, 25 years. 

If you're looking at a debt service loan, 15% is the minimum for a purchase but it's much more common (and rates are better) at 20-25%.