Current Loan Balance: 100,952Interest rate: 3.75Mortgage payment + insurance/taxes: $1066Rent: $1500/monthEstimated current value: 227k Current cashflow: $369/ month, I also have a first american home warranty on it $68/month so after everything I net about $300/ month. 

My mortgage payments are currently $2,841.40/month and my property management fees are 4% (I'm striking a deal with a property manager I trust so I'm super thankful for them giving me such a low rate).

The interest rates are too high, the projects always run long, and you will deplete your margin by using a construction loan.  

It'll tell you a $500k conventional mortgage was recorded in July 2021, you can infer from the ownership record that it was a refi (same owner before/after), and you can ballpark that rates were around 3%, assume it's a 30YF, so the balance "should" be X, but you have no way to know if they made a large lump sum payment, pay extra each month, etc. 

We have a interest rate around 3% on the SFH, purchased in 2021, so doing any refinancing with that doesn't seem to make sense.

According to HUD Fair Market Rental Rates for 2024, the market rent for each unit in the 34608 zip code is $1,700 per month.While the units are in good condition, consider updating the kitchen, bathrooms, and fixtures and adding a fresh coat of paint for a fix-and-flip strategy.

We are choosing new build because A) our family 4 has a certain size demand B)  the price-quality ratio doesn't seem to make sense when considering a preexisting home C) with interest rates being at near 8% with preexisting homes, builders are offering 5.99% interest rates and the exact home we are looking at is about $75K discounted because it's a spec home and the builder doesn't want to pay taxes on it.So, live in it for 5-6 years hopefully rent it out with a fully finished basement for potentially $4,200 in 5-6 years.

What loan type (DSCR or conv) should I be looking at and what rates?.

In the 80s interest rates used to be double of what they are today and people still succeeded.  

And vacancy rates may also increase because of the amount of bureaucracy you have to go through to place a new tenant.So again, a lot of variables.