When I told him he would be responsible for a fee to break his lease plus forfeit his security deposit, he is reconsidering, still haven't heard a definite answer.  

His move out slip indicated he had to forfeit his deposit and he owed an additional $2100 dollars in damage.

If that amount meets or exceeds their security deposit than they forfeit the entire deposit.I agree with @Michael Sato, and you can't do it soon enough.  

I personally couldn’t imagine forfeiting so much to taxes or any other built in regulatory measure in the state.

Obviously you’re forfeiting a lot of nice owner occupied benefits, but if you weight the pros and cons then you may find one is better than the other for your needs.

If you miss a deadline, or don't do something in exactly the right way, you could forfeit the right to be paid anything at all. 

If they move out before the date on my notice, they forfeit the right.THEY CAN PAY THE SAME RENTMy greatest concern is that after spending 15k+ renovating an apartment, that the first right of refusal allows them to move back in and keep paying the same rent.

@Glen DoeringDumb Luck is the best way.There are many factors, best are those with a combination of factorsConditionvacant and or boarded uplarge lien relative to the value of the property, large lien relative to the assessmentOwned for a long time 20+ yearsowned by a forfeited companyOut of state ownerAbsentee ownerNo or very small mortgage on propertyMortgage that is a bank that has gone out of business or acquired by another bank.Estate ownedAs you can see some of the same things you would look for in any lead, tax sale or not.

If you  are using your place as you describe you will be forfeiting 50% of your rent potential. 

If you do not purchase by date 'x', this money is forfeit to the lessor for your default.In essence, you seem to be looking to live rent free with no downside to you, only to the current owners.Now, a lawyer on behalf of the owner might be able to make that work for you.