I know I have to honor any existing leases (assuming there's no language to the contrary in the lease agreements).

If you lease a system, the 3rd party owner (leasing company) gets the tax credit.

If you lease a system, the 3rd party owner (leasing company) gets the tax credit. 

Their lease is coming to an end in September and we're not going to renew it nor are we going to allow the tenants to sell the business.

Their lease is coming to an end in September and we're not going to renew it nor are we going to allow the tenants to sell the business.

Review their lease agreement and addendums.

Yes, only thing you need to come up with is a property for sale with tenants in place, or a property that need extremely little rehab and signed leases.

Homes where people have paid thousands in rehab where nothing was done.Situations where the owners have been receiving $700 in rent each month, but the lease with the actual tenant is much less. $450 in one case.

And most importantly, in your experience, does national tenants move that swiftly within the seller's 45 day due diligence period and offer their LOI to lease the property since they must do their due diligence as well?

I had an allure ultra click lock floor in a retail store for two years and when we lost our lease I pulled it up and installed it in a rental.