So he would fund the total amount minus my down payment.What are the legal ways to do this so that I can buy 2 properties from him, he can sell them, and still use those sale proceeds (along with the sale of the other two duplexes) into a 1031 exchange into a commercial retail property?

Do you have MLS access yet?

However, (a) there are IRA/401k compliance concepts that you should be aware of and (b) you should develop an efficient method for accessing IRA capital - I'll often get introduced to syndicators that find dealing with IRA/401k money to be a huge nuisance, which it does not have to be.On most syndicated deals there will be leverage involved, resulting - potentially - in taxable UDFI to IRA investors.

Other than the tools they have access to, how do I know if I can trust them in looking out for my best interest?

My goals are to start with some fix and flip rehabs, possibly wholesales and leverage my way into multifamily and eventually commercial buy & hold properties.

Warner Robins has interstate access so you could branch out a bit.

If the guests arrive at noon but the particular condo is not ready, I sometimes give them the parking garage passes early as well as access to the pools or beach sets.

I'm a home owner and have some commercial real-estate. 

I have not gotten any Fannie/Freddie financing only commercial loans.  

Access to a pool?