Buying property with tenants already living in there

[Darren Fryson]

There is a property that popped up it's cheap it is two buildings on one lot. Both have tenants currently in them. The unit as a whole generates 1100 a month. 

I'm wondering if the reason the unit is for sale, is because they haven't been paying rent and the owner just wants to dump it. How do I check or verify that they are current on rent? I know I'll have to redo their leases. Should I do a price increase?

I'm thinking the extension of the eviction moratorium has something to do with the discount. 

How do I make sure the place isn't a total pile that I'll be dumping 1000's into? 

Is there landlord insurance I can get that will cover rent for like 90 days if they just stop paying?

like I said tons of questions? I'm sure there are a bunch I haven't even thought of.