It sounds like the Title Co. was not aware that the tenant prepaid rent and just prorated the current rent for the month of closing, so agree if they had no knowledge of it, would not have ever gone on the settlement statement as a credit to the buyer and they likely will not do anything post closing to help obtain those funds. 

That's a house of cards ready to fall down fast. 

you can always call or email the tenant in regards to this matter. i personally smoke as well and just would want my tenants happy and not feeling accused as its a big problem with a lot of tenant v landlord situations around the country. you can always say you got a report of the odor of weed and was just verifying the smell with both tenants on the property. you can restate your conditions with smoking. you can always ask if they are legally able to do so as well (meaning medical card). depending on how you want to handle it, if you want to make it a legal warning to the tenant as well, you should write a written letter sent by mail stating you got a report of weed and this is a written warning in case this a problem down the road, you have evidence to show the court if it gets to that matter that this is not your first occurrence. best of luck!

Also credit score 680 with no missed payments over the last 2 years and also check their criminal report just to make sure you know who these tenants are, as the eviction process in New York city is very long and expensive. 

Based on your numbers, and assuming you have a credit score high enough and have never filed for BK, you shouldn't have an issue getting approved for an HML to buy/rehab the property that I would estimate at about $370k-$375k (which includes 100% of the rehab costs).

For us we all typically use 0% business credit cards to furnish the property which can amount to $40-$60k+ depending on how crazy you go. 

They have no credit history, so you have no idea how responsible they are financially.

@Angelo LlamasAt the bare minimum, you should do the following to make your bookkeeping easier:- Dedicate one checking account and credit card exclusively to real estate.

I was working with a local credit union who pulled out at the last minute.

The guests have a credit card on file and your policy should allow you to charge for damages or excessive cleaning.