The "convertibility" only locks in your insurability.

It's tough to time it right on, but since we're not anticipating any huge gains, I don't think you'll leave much on the table if you pull the trigger a little early.  

The fee locks in their rental rate, purchase price, and reserves the property for them to have the option to buy so you cant sell it to someone else during the option term.

I'd like to get a purchase/sale agreement to him asap to lock the deal down because I don't want to give them enough time to tell anyone they are selling it and receive a higher offer on it.

I also, gutted the semi-finished basement as there was wood paneling against cinderblock walls with no wet lock or sealant (causing white mold in some spots).

Whatever you buy now is locked into that rate for 30 years.

And since interest rates are still relatively low historically you've locked in a good rate for 30 years.

The fee locks in their rental rate, purchase price, and reserves the property for them to have the option to buy so you cant sell it to someone else during the option term.

What I'm unclear of is if I'm a new investor how do I do that but protect myself from getting locked into multiple purchases when I'm only looking for one at a time without ruining the reputation of a broker or myself, or getting into legal problems?

As for showings you can schedule them with proper notice but at this point are you comfortable renting knowing it's probably not going to be vacant..If they chain the door shut or have changed the locks your not going to get in.. and more than likely if you do the place will be a utter mess and they have given you every reason to believe it's not going to be easy..