If the $ is big enough it might make sense to consult with an attorney to determine if this was handled properly by the seller/condo association as concerns prospective purchasers.

I am choosing to save up some capital until I can afford to handle mistakes, before I jump into a 6 figure decision.

Environmental companies can perform an assessment called and ESA or "Desktop Review" its a historical record search that ties into a number of databases that will know the history of that tank if their is one, who put it in, and if it is still deemed "hazardous or dangerous" to the public.My company is an environmental firm that handles these types of issues in the commercial and residential real estate industry.

He handles pretty much everything for me in regards to any legal stuff for my real estate.

With origins in the 15th century, it belonged to D.

That comes first.If your tenant has done any damage, it's already happened and it's likely not as bad as you are imaging.Some areas have eviction services where you can hire someone to handle the entire eviction process for you, from the very first step of filing and serving notices, to the court date, to the eviction day itself.

But if it is something you and your wife can handle then go for it.  

I am a Realtor so I will start with saying that you can always list your home with a Realtor, but I am guessing that you want to handle on your own so I have a few other tips. 

How should I handle future interactions with this tenant and her husband?

The jump from 20 to 100 can happen fast if you can show investors you can handle their property in a professional manner.