Tactics like that would absolutely ruin your reputation quickly.  

While the cost of material is higher than carpet, the installation is fairly easy and if a piece gets ruined, you can just pull up that one piece and replace it. 

You can also be lead or lead yourself to financial ruin in ways you may never be able to recover from. 

When your new you are more likely to make mistakes and having a loan against a project like that can ruin you quickly.

It will keep the brushes wet up to a day ro two... might ruin the brush though.

It may ruin the friendship.

The woman sounds persistent.Hindsight is 20/20 but it sounds like a 24/7 security guard or a live in house watcher would make sense.When they finally remove this woman, they will find that everything inside that can be ruined, will be ruined.

I plan on purchasing another home soon i would like the opportunity to use the loc if necessary. i dont want to ruin my dti by adding another payment before applying for conventional financing.Does a HELOC with a zero balance show as a 0$ payment and not count towards my DTI?

In one case where tenants had stained carpets to the point of ruin I did rip them out and put in laminate.

there is a difference between renting an appt and renting a house. houses are more expensive.also, sounds like you dont have the best relationship with the inlaws. a sure way to ruin it further is to become their tenants. i'd run away from this "offer". far away.