If you use the listing agent, their duties will still somewhat favor the seller whom they have a longer relationship with essentially, so why not find your own representation?

It’s a huge tourist market, it’s near the beach, it’s drivable to a large portion of the US and the laws are favorable.

Our concern is two-fold (1) it may be difficult to get a loan given that both of us would be considered contractors and I know banks wouldn't look favorably on that, and (2) just the overall fact that both of our incomes would be commission-based.  

If you go that route, do yourself a favor and do not shop it around yourself.

While the numbers may not be favorable for some, the important part is that you guys took action and the deal is working for you.

I do my own calculations using 3 similar properties sold in the last 3 months within half a mile of the subject property and I can pretty much come up with a "favorable" number if I'm buying, depending on which 3 properties I select and a "favorable" number using a different 3 properties if I'm selling.

If I could find more favorable financing,, it might work.

Honestly, if you can get land in the path of progress, at favorable rates, and have a long time horizon (5+ years), just close your eyes and go for it.

If you're looking in any major market in Texas, this is only amplified because Texas seems to be the preferred stomping ground of many investors due to the favorable laws. 

Just came back from a SFH I did repairs on in a nice area  .I hired out the  dry wall work good buddy .I fixed doors,deck ,bathroom issues that saved me 200 or more .The drywall work might be free he owes me a favor no biggie  either way .