Pre-construction are the best deals in that you can buy much cheaper if you buy early enough, which gives you a much higher ROI and give you equity from the get-go.

I am a broker helping people buy.

We'd love to buy low and add value, but if the numbers seem to work on a turnkey property, is there a reason not to go that route?

One other thing is that I paid a lot in points to buy down my rate which made the mortgage initially expensive… It will also take a while to refinance (a couple years) so I don't want to wait fully for that option eitherIf my tax rate is 30%, is it right for me to think that the cost of paying interest is ~5% instead of 7%?

It depends on the number of properties you want to buy.

My wife and I have been buying, flipping and renting for 15 years.  

I'd rather try to retrain them and keep them then have a turnover right when we buy the property. 

I have expanded one park but purchased 9 overall and I will tell you that you can get a much much better deal buying existing and scaling it.New parks are extremely time-demanding and take a lot of capital.

I'm also looking at the area like the OP (evaluating a potential buy and rent here), but not familiar with conditions on the ground.

I have been saving since I was 14 years old, and I am on Track to buy my first Duplex (house hack) while still being a senior in high school with my Parents cosign, I turn 18 In a few months.