They persist even when I explain that if they can't speak English they can't sign the lease.

The lease should stipulate the the tenant is responsible for taking care of any accumulation of moisture and required to notify the landlord in writing if the problem persists.

Finding the opportunity isn't obvious or free, per se, but there's no reason you can't leverage your networking or dogged persistence to do it.Money, Opportunity, and Execution form the triad of a successful investment. 

Why do you persist in keeping bad tenants in your houses? 

I was unaware that the situation had supposedly persisted until now.

I admire your persistence and not giving up and holding your property as long as you have.

If he tells you that there are no bedbugs, which is damned hard to determine with any degree of certainty, then you find the infestation persists, he could be held accountable for your problem.You might talk to the inspector to determine if this is his real issue.

In the end, we would rather have someone called pre-maturely than a potentially damaging (i.e. overflowing toilet) situation persist.

If you want it bad enough, and you buy it right, I'm sure you can figure it out, it might take a little longer sometimes since you're not local, but keep being persistent and don't get discouraged!

If they persist on wanting more money, tell them that your understanding is that what you've offered them is actually generous, but if they want a judge to decide that's up to them, and you'll be happy to abide by whatever a judge decides.