Doing it this way may not be monetarily the best way to do it but it works better because you get a psychological reward of paying something off and it will then give you motivation to pay off the next. 

Hi David,Welcome to Bigger Pockets!

Your debt to income is really not a deal breaker you have to shop around for financing, the Brrr strategy is something you may want look at there multiple podcasts on bigger pockets regarding it;  Your definitely on the right track keep asking questions and take action!

My target is to find 3/2 (or bigger) homes in B-/B+ neighborhoods.

A 20 year initial lease on a business that is growing in an industry that will only get bigger with a strong lease guaranty would have a significantly lower cap rate than a 10 year lease with a struggling company you're looking to turn around.That being said... as I started: I don't believe you are being unfair.

Next, the Sponsor is rewarded for the asset performing very well with the 80/20 and 50/50 split.

In that case you are leveraging his expertise reducing the risk and also you ll be able to afford bigger deals with more capital and its a win win situation.

Just saying its a bigger world than presenting a hard and fast rule implies.

Bigger pockets has some great tools to help you calculate the cap rate for a duplex.

For a bigger spot like yours, I don't think traveling nurses will be able to afford it, so you're going to need corporate travelers or maybe rotating doctors (if you're near a hospital) and like @Myka Artis said, I'd be looking at CHBO and furnishedfinder.com for that.