Make sure you have great disability insurance (Guardian is top notch), a great umbrella insurance policy, and an LLC with a thick corporate veil (and great property insurance). 

You could always use those to prove they were smoking up; with that proof you can either move to evict or simply hold security and at least have some sort of proof.If you install a marijuana smoke detector I wouldn't even tell them what it is (aside from a smoke detector) as they might try and disable it.

And unfortunately even poverty level, single mothers, with disabled children.

I am also waiting on my VA disability which will act as another source of income while allowing me to qualify for the VA loan, yet that is a wild card option.

The goal is 10% or higher disability.

Familiarize yourself with the Fair Housing Act, which prohibits discrimination against people with disabilities, including those recovering from substance abuse.

However if they are on limited income, military disability, SS, pension and they are currently paying a similar rent, no major other payment, I will waive the requirement.

And depending on the veteran's disability rating it could be as high as 3.3% of the loan amount.  

The problem is their only source of income is the husband's medical disability check.

Case workers look at things such as disability, are the potential tenants collecting food stamps, child support, do they have other income, SS, how many children, what ages are the children etc etc etc.....In your earlier comment you said average for 3bedroom is around $900.