Found a 1987 covenant on the retail box that says no residential use. Now what?

The unidentifiable LLC is the whole deal. If they hold the largest pad, 75% by land area probably can't be reached without them, and you have no idea what they want. I'd spend $200 of the $4,500 having someone pull the LLC filing and the deed chain first, and decide after you know who you'd be negotiating with.

Seller saying "probably unenforceable" is the seller telling you they already asked someone and didn't like the answer. Ask them directly whether they've ever tried to get it amended before. If they have, the paper trail exists somewhere.

Separate from the covenant, run the parking math both ways before you spend a dollar on lawyers. 5 per 1,000 on 30,000 feet is 150 spaces you have to keep. If your residential plan needs 1.5 per unit that's 36 more on top, unless the city's overlay lets you count them together. On a job I did with a shared parking field the surveyor found the striped count was 118, not the 150 the document said, which meant the seller had been out of compliance for a decade and nobody cared. Doesn't make it legal, but it tells you how alive the document is.

Also 22 foot bays and clear span single story means you're building everything from scratch inside a big shed. That's not cheap just because the roof exists.

I'd walk. You have 21 days, three counterparties, one of whom you can't name, and a document with no sunset. That's not a due diligence problem, that's a two year project you'd be starting for free with no control over the outcome. There will be another building.

Whether that use restriction is enforceable turns on state law and on facts specific to the center, so it is a question for a real estate attorney licensed where the property sits, and the answer changes by state. What you can do in 21 days is narrow the question so the legal work is cheap.

Three things determine what the covenant costs you. First, who has standing to enforce it. Some declarations grant enforcement rights to every owner in the center, some only to a declarant who may no longer exist, and some to a tenant by separate agreement. Read whether the 1987 grocery tenant's lease had its own exclusive or use clause that survives independently of the declaration. That is a common trap, because releasing the recorded covenant does not release a lease covenant.

Second, the amendment threshold. 75% of land area with three other owners means you need to know the exact acreage of each parcel from the plat, not from the assessor. Run that number before you assume the unknown LLC is a veto. If the bank branch and the auto parts store together clear the threshold with you, your problem shrinks to two conversations.

Third, the parking obligation is usually the harder one to amend, because the other owners get real economic value from your spaces and will price the release accordingly. That is a negotiation you can partially underwrite. Price what it costs to keep the full 150 count with structured or relocated parking and see whether the project survives it. If it does, the covenant is just a cost line and no longer a wall.

Your $1.1M price only works if the covenant clears. If you cannot get it under contract as a condition, you are paying a clean price for an encumbered building.

Extension with the earnest money staying refundable until the consents are in writing, or nothing. Sellers of tired strip centers are usually not fielding other offers. Ask.

@flint's version is what I'd push for, with a specific tweak. Make the extension conditioned on the seller cooperating, meaning they sign the letters, they make the introductions, and they pay half the legal fee. If they believe the covenant is unenforceable they should have no problem funding half of proving it.

What I'd also do is pull the last three deeds on each of the other three parcels and see whether any of them already got a use amendment. Centers like this get amended piecemeal all the time. If the bank pad got a drive-through variance in 2004 that required consents, someone already built the road you're trying to build, and you can copy their route.

@bramble named it. Cut courtyard is what makes the floor plate livable and the parking covenant is what kills the courtyard, so those two lines in the document are actually one problem. If I were you I'd have the architect redraw with the courtyard on the back third where the loading dock is and see if the parking count survives. Ten days of drawing beats twenty-one days of lawyers who can't move the other owners anyway.