@Ned Carey Both properties I purchased were vacant for many many years and required full gut rehab to be inhabitable.

Hello BP,I have a co workee who is looking to sell her land she owns a few towns away, she haa about an acre of land and a house that is "inhabitable".

I have walked into a couple properties and two strong emotions come to me: i) just felt like there was no way I would live in those properties and ii) i had no idea how much it would cost to get it to a minimum level of 'inhabitable'.My main question is: How can I quickly 'calibrate' myself to be able to reasonably estimate costs of home-improvement job(s)? 

That provides a unique position for us, our inhabitants, and our housing market.If you want to assume very little risk, there is no harm in waiting a year to see what pans out.

Nothing is so bad its inhabitable but new windows, redo the hardwood floors, some drywall need to be repaired, paint and we were thinking of putting in ductless a/c since it only has window units. 

Maybe you could help him move by stating the unit is inhabitable and you need to make the necessary actions to bring it up to health code and so he will need to vacate.

This actually happened in my other unit, however the students co-inhabited for a month and it worked itself out. 

My son has been spending time there recently and thinks it shows a lot of vitality in the diversity of its inhabitants, as well as the mix of rural lifestyle with suburban amenities.

The more people which inhabit a unit, the more damage which is likely to occur.

Now the same criteria must be applied without regard to the age of the inhabitant.