In general I find the financing options to be DECREASED by owning a property in an LLC.   

My money will be going to start LLC.

As for legal entity it depends on what’s most important to you - I my self just incorporated under series LlC.

Will I have to start with a LLC ?

In the ones where I'm the investor/partner we use a pretty standard structure, cap mgmt llc, partnership llc, pass through on K-1 etc... 

@Jack McWatters If you would qualify for a loan to build a 350k house you should easily qualify to buy the land.A credit union or bank or google land loan,some companies specialize in that type of loan.If the land is paid for it’s not too tough to get a construction loan to build the home.With carrying costs excetra It may not be that great of a deal.Since you asked about Private Lenders the best thing to do is to talk about what you do to everyone you know.Dentist Doctor friends relatives and tell them to pass it on.I have owned an LLC for two years and still have relatives say ( I didn’t know you bought houses)smhBest of Luck!

Also, I believe I meet those other requirements, such as purchased by an LLC, keeping of clearly separate records, etc.

Also as you mentioned they have to be coded correctly, so that can be an issue as well.As you mentioned you might also set up a key word search to get more or different listings.If your MLS requires owner name to be input, you might also search or *bank* or *LLC*

Is there a way to transfer the house to an LLC at this point?

I don't have any LLC, so am not the best person to ask about that.