Getting closer to Deal #1 - monthly payments freaking me out!

[Obaid M.]

Hello BiggerPockets! I'm getting closer to my Deal #1 seems like (closer than I've ever been)...and I'm getting a bit nervous thinking about monthly payments I'll owe to the lender. 

The property I'm looking at is currently 70% occupied. One of the 4 tenants has less than 1 year left and there are two units currently vacant.

What if somehow none of the tenants renew their leases and I'm stuck with this huge payment that I'll owe. I know every business has its risks - am I worrying for no reason? This is a 12 year old commercial property. Couple of the tenants have been there a long time. About 3 years ago property was 100% occupied I'm told. 

Am i worrying myself for no good reason? How do I verify past occupancy information? What is the worst case scenario I'm looking at if property goes to 100% vacant?