I sent her a letter to get rid of the cats.

If you have 20 properties to evaluate, you can get rid of a lot of the weaker ones by applying the 50% rule, the 1% rule, or whatever method you've developed for your personal standards and your local market.I use the 1% rule which states a unit should rent for 1% of the purchase price.

We did that for a year, I worked tons of overtime, and with that we were able to buy a couple more properties and then look to getting our "real" home that we live in today.I found that getting rid of all of the pre-conceived notions of "I've earned this lifestyle" was what allowed me to really focus, and that made it even juicier when we bought our new primary... it wasn't a small step up, it was like flying to the moon!

If it's a low-class property but in an upper-class neighborhood, I would see this as an opportunity to increase value and consider moving forward with the purchase.You can't just "clean" an apartment and get rid of bed bugs.

I'm currently rehabbing a 3-fam and getting rid of any K&T I find. 

Get rid of the knob and tube though.

If not, then you  may end-up removing sections of subfloor.We've had a post dog renovation (after 9-years) that required a full gut to the studs and slab and a complete rebuild of the apartment to get rid of the stench.In the future, either do not allow pets or check-in on your tenants more frequently.

If you had inspected every 6-12 months, this wouldn't have been so bad.You have to get rid if the tenants before you can properly fix the problem.

Big negative for the house is that the current owner, a retired gentleman who is a smoker, has therefore made it smell like an ash tray (was painted in the last few years, so no terrible stains) and therefore will get rid of carpet and replace with laminate, and seal and paint throughout.

It is most likely in the carpet which is tough to get rid of.