Though, that would probably be a similar cost to the above ground pool. 

You need the backup option in case the mid-term rental market changes.Minimizing turn costs and downtime is critical.

You would end up saving the higher interest rate on the HELOC as well as closing costs.

Little background behind the door: It's a MDF cheap one you buy at HD or Lowes. 

Even with buying down the rate, I would not expect to get better than low 6's in the best of scenarios.

Get replacement cost hazard insurance along with an umbrella policy of at least $1M, probably double in your area.

Conversely, a new built A class SFR, in A class market of significant growth via a well laid out planned city development, great schools, area people are glamouring to move to, a-class tenants, very very low risk.

Typlcally, a lender is going to lend 75% - 90% of the Cost of the project (property price plus rehab cost (scope of work)) or 70% - 75% of the ARV (As Repaired (as completed) Value).

It costs me $1,500 to evict a tenant with it usually taking two-three months.

To be more specific about what i'm looking to do: My 1-2 year goal is to employ the BRRRR strategy with SFHs and Condos by buying distressed / highly undervalued properties that need work (preferably all-cash) in low crime areas with strong rental demand, renovate them within budget (again preferably all-cash) and get them rent ready before refinancing them at the highest ARV possible.