I was given notice that the rent was going to increase once my lease expired. 

I inherited these tenants and their current lease which expires in April does not have any language in there to help me out. 

The high bidder was bound by the lease for the next almost 30 years, before they could start to collect rent and they can't evict the tenant because they already paid their rent to the former owner.I saw a property sold at tax sale that was an expired lease for a building already removed from the site. 

(Not legal advice)From your post, I understand that this lease is to expire on January 31, 2018.

Make sure to stuff it with #hashtags, share to groups, ask people to like & share as well.9:00am –MARKET TO EXPIRED LISTINGS- (1 hour) Lookup the expired listings in a certain zip code over the last 12 months and send out a letter to the property owner.

Make sure to stuff it with #hashtags, share to groups, ask people to like & share as well.9:00am –MARKET TO EXPIRED LISTINGS- (1 hour) Lookup the expired listings in a certain zip code over the last 12 months and send out a letter to the property owner.

You may not be able to raise rent at all until their lease expires.  

3) Should I run a pro forma and assume rent increases (6 of the 8 current leases expire this year) and base my offer on what I expect next year's NOI would be?

I called my handyman a couple times last week for a couple different jobs, like installing expired fire alarms (on really high ceilings), and an under-mounted sink that had fallen.

The option is expired, but tenant still wants to buy.