.- how much time/effort are you wanting to put into this? 

If that's the route you wanna go, you should expect to pay the contractor a flat fee for his time and effort.

Even if the market for rental housing is tight and tenants are lining up outside the landlord's units begging to move in - at least in Ohio - if a tenant has to break a lease the landlord is likely to get only the security deposit (though they are often entitled to more) and the landlord has an affirmative obligation to mitigate the damages by making a good faith effort to lease the unit. 

We have not decided where to concentrate our efforts, that said we have a few potential possibilities, Houston Tx., Kansas City Mo., Detroit Mi. and we are looking to include Florida locations as possibilities also.

I am putting all my effort on now learning as much as I can about REI!

I wanted a honest answer on whether or not wholesaling real estate is a lucrative business to enter, I want to know before I spend a large amount of time and effort learning this investment technique.

@Jaron Smith usually the crawlspace is a ventilated area, so unless you plan to dehumidify the neighborhood I would'nt waste the effort and money to install anything in there.

Despite my efforts to mention soundproofing, separate entrance, etc....., I'm unable to get her onboard.

Acquisition by adverse possession is more urban legend than reality, and of the real aspect of it, it requires materially more effort than "filing a claim".

You are the only one who can ascertain if your time and effort are rewarded by the payout.Just my two cents...Wish you the best with this.