Set a 45day due diligence period and then use that time to secure a Long term NNN tenant.

It's a good thing that you were smart enough to do your due diligence first.

How do you pay for and time the various due diligence reports that need to be completed during the due diligence period of an apartment building being under contract? 

Take ownership of your mistake and learn to do the proper due diligence recommended above😊

During due diligence you will inspect each unit. 

@Olivia Hardy If you have done your due diligence, numbers made sense and you have a solid team that will be looking out for your best interest at all time then proceed. 

Highly recommend to NOT DIY it - not just the legal side, but everything including due diligence, funding, acquisition and operation.Peruse the Multi-family forum here on BP, buy some books, and most importantly - get a mentor or a partner.https://www.biggerpockets.com/forums/432-multi-family-and-apartment-investingYou will be risking the money belonging to other people, and it's a huge responsibility.

You will never have access, you might not know of all the liens at the time of the sale, you will not know if the owner (or tenant) is a holdover and not leaving, you won't know much of anything unless you have the lists in advance and do your own due diligence and door knocking and investigating.

I'm trying to systematize my analysis/due diligence process for flip properties.

Hence, the assumption structure.After completing due diligence, it was apparent the expenses were very high and tenant payment history was less than ideal.