You offended them, and is natural. 

If the property is in an area that you believe will appreciate one day (arts district, natural appeal, etc) and will also produce positive cash flow, then I don't think anyone should fault you for taking that deal.

If I was representing a tenant, I would argue that the landlord --- you as a natural person --- cannot evict the tenant since you do not have a rental license.

In other words- do we take a 40-50k profit now, or wait fifteen years to sell with a stable rental property, principal pay down, and natural appreciation? 

I also enjoy spreadsheet cranking (I do data analysis for living so I guess its like my second nature...?). 

But with the following checklist, you can make a better determination of what that house is truly worth, and if it is the right deal for you.CompsComps, or comparable sales, are the natural starting point for determining property value.

Given the archaic nature of the properties in and around Boston, most properties have this and what most people do is to cover it up.

As @Bryan Zuetel mentioned above, you will need to provide the details of the type and nature of occupancy to your attorney to begin the process.  

I meant to add that hydrostatic testing is most commonly used for natural gas lines.

I am going to a direct lending originator with the agencies (Fannie Mae, Freddie Mac, & HUD), mortgage broker for financing all other financing options, and an asset manager / developer for a family office so please consider the nature of those businesses (investments in real estate, etc.) as a factor as I would assume that would have an impact on the decision.