I found for almost all financing of manufactured homes (that's technically what they are if manufactured after 1976) that the issues can be:  what kind of foundation are they on (is it concrete or just a gravel pad),  how many owners has it had or has it been moved more than once, and age.   

Humidity levels in basement is high at 64%A/C was 40 years of age, not functionalSigns of Ice damming on the garage sheathingFurnace is 19 years of age, unit didnot fire when turned on at the thermostatThe incoming 3-wire electrical systems is considered out of dateNo GFCI outlets anywhere (including in Garage)Walkway has cracking and settlementGarage floor, concrete has typical cracking and settlementBasement floor, has signs of cracking and settlementKnob and tube wiring in the home is considered obsolete and may pose an increased fire hazard.

Concrete floor and drain system? 

Concrete delivery was 3 day wait .

Thanks for some useful, concrete suggestions!

So they can visit relatives or work at a job.If it fills up, build more concrete tilt up row houses. 

I know the building market is crazy right now with labor and materials, but if anybody has a good concrete/foundations crew that is looking for new work please let me know!

I doubt that's the case here, but if you don't rent to them I'd document concrete reasons why, both to them and in your own notes.  

Foundations - building foundations, pouring concrete, etc2.

Steel with concrete treads?