Family planning to move in has 2 adults and 7 kids and we don't think the house can handle 9 people especially the toilet/bathroom with old sewage/septic system.

The advice below assume you're an adult.

I’ve probably learned more from reading books and taking courses as an adult than I ever did in any public school system, excepting private business schools which were excellent too.The most expensive course I ever took was the $5k Robert Allen protege course and frankly the best I ever took.

Tenant has adult son that lives in the appartment.

I have to explain what the title company is, and why we use it to protect both parties.Seriously, I've been a sales guru most of my adult life, and if not for being honest and having integrity, I could get 99% of adults to sign a blank contract, then tear it up and tell them how stupid that was, and why they should never do that, then 15 minutes later I could get them to do it again...

I have lived in the Medical Center for most of my adult life as I did my schooling at the University of Houston.

So many Landlords treat tenants like babies instead of like adults. 

Most likely he is an expert on whatever his perseverations are, and if you have a question about about his special interest,if he does not know the answer he will research it and tell you]Our 'weirdness" is why we are treated as "less than" to such an extent that for those of us who are Autistic, 95% of us [ both male and female] have been sexually abused [ being too weird to be human makes it okay to those who hurt us I assume] and we are 28 times more likely to attempt suicide. 

Like you, all adults (age 18 and up) must fill out a separate rental application with application fee.

Some people are just more direct than others.Looking back over a timeline and the number of expanding issues is giving me pause including; not paying the upfront money when required, both parties not coming in to sign the lease when arranged and now getting a request that the number of occupants will be expanding from 4 adults, 2 animals and 1 part time kid to 6 adults, 3 animals and 1 part time kid.The house is a small 4 bedroom cape so this new requirement isn't sitting right with me and now I'm kinda glad that they put off signing the lease as I am considering telling them thanks but no thanks.I don't have a backup tenant lined up so it may take a month or so before I can get someone in there but I am concerned that it may be better to take the revenue hit now than deal with their issues later.Any words of wisdom?