Coop listed with two addresses and one BBL?

You're buying shares of a corporation, not a piece of real property, so the street address shouldn't make much difference. What you need is the address that the co-op corporation uses, and the description of the unit as contained in the proprietary lease.

While you may end up purchasing the shares from the seller, there's no guarantee that you'll be able to occupy the unit without co-op board approval, so your lawyer needs to make sure that permission is either included in the terms of the sale, or is otherwise granted.

Thank you. That advice makes sense.

Is there any way for me to get that info (proprietary lease, the address the co-op corporation uses) online or from a government dept? I've been calling as many people as I can and asking around, but it hasn't led anywhere yet.

I should also mention that, confusingly, the two different addresses have two different UCC1 liens for approximately the same amount that include rights to the proprietary lease attached to the address. But both addresses are attached to a single BBL.

Go to whomever is representing the seller (possibly the bank doing the foreclosing), and get the terms of sale from them, which should describe just what it is you're getting at foreclosure. Go to the managing agent, tell them you're doing due diligence on the planned sale, and ask if they can provide a copy of the proprietary lease for the unit, the co-op house rules, a record of their liens against the unit/shares, and anything else they would like to provide to help return the unit to a proper upstanding, maintenance-paying member of society. Hand all this to your lawyer, and have him/her explain why you should or should not proceed.

Yea it's v possible. The seller may have not legally combined the units. Especially prevalent w condos, where adjacent units have been combined, but not legally. So they still get two separate property tax bills etc. Lot of tax implications

There're quite a few co-ops with two addresses. E.g. 31 E 70/30 E 71, the Millan on 67th/68th, 15 W 81/16 W 82, and all those multi-building co-ops.

The UCC1s, etc., might use one or the other address. The name of the co-op will be on the UCC1s, and the city's DoF tax site will have the address it uses.

Make sure the loan is actually on both units. I am aware of a case where someone bought 2 condo units and got 2 separate mortgages and then combined the units. The first unit got foreclosed on, was purchased at auction, and the purchaser couldn't even successfully evict the former owner because they didn't own what was currently "the apartment". One way you could check is to look at the Schedule A and make sure the number of shares being foreclosed on matches that of both apartments.