Doing it the opposite way will likely waste time and money, and require you to find a unicorn lot for you predesigned build.If you strategy is to build to rent, than you should focus on that.

My plan was to sell the property next year, but wanted to pull some cash out prior to selling to help minimize the capital gains tax.Is there a proper name for this type of loan product that I should be looking for?

If they have never done a MHP loan, don't waste your time. 

It was purchased as a turnkey property that could be rented out with minimal investment.

Setting up a MLS listing (although one with certain criteria - requires a concierge level service) is minimal time; but driving to see property (DFW is not a small city) takes time with pre-research, scheduling time with you, post-research, etc.

I am confident that my wife and I can retire on a reasonable income within 3-4 years through investing in real estate since our 9-5 jobs provide an exceptional amount of capital as long as we don't waste it.

You can save time though by getting a feel of where the seller is at before wasting time on a walkthrough. 

The waste line will be more of a challenge, but certainly doable. 

We wanted a nicer property to minimize maintenance headaches and to attract a higher class of tenant and therefore new construction was recommended to us.

Finally at the end of 2020 my wife told me; "you are just wasting money on this".