If I were the investor/builder, I would take a big profit as I will be thinking there's something wrong somewhere, someone selling land+permit is great but I have to ask myself, why would someone go to that kind of trouble just to not build it, i mean, practically that's the easiest thing to do after the permit.

We are interested in learning different successful real estate investing practices in Baltimore.

Best practice is to understand the law and act in a prudent manner.

Even if I don't end up saving money vs. the original offer, probably doesn't hurt to "practice" being aggressive in finding competitive financing...

As someone who practices law in disputes between contractors and homeowners in Nashville, it sounds like you are past the point of anyone being able to help you on a forum.

This practice of renting by the room is very common in college towns; you can probably get some good ideas from the websites of these type of rentals, including rules, applications, & leases.  

Read all that you can, but also put what you are gaining into practice.

A few practical things you can do in your situation to build your credit and start investing might be to get a CD secured loan at a credit union or bank.  

It takes practice and many years of experience to perfect the process.

Practical question: it's easy enough to figure out what cap rate the seller is using to determine their price (if they don't state it outright.)