My question is, do I need to amend the last 3 years worth of tax returns to correct this small issue, or can I just input the correct amount on Form 8582 in my 2021 tax return going forward? 

In addition to wholesaling, I also do condo-conversions, parcel reconfigurations, zone-lot amendments, and re-zonings for buyers on properties I have sold them or sometimes on properties I did not sell.

If that is the case, you may want to speak with a CPA about filing an amended return with only a single Schedule C for all your endeavors. 

The law also stated that CC&R's did not need to be amended until December 31st, 2021. 

@Adam Romano, I would check with an attorney to see if you can amend the current LLC to add the Private Investor. 

As the lease is already signed, how do I amend it?

This is what the woman's lawyer stated:"To begin, "man" cannot unilaterally modify and/or amend a lease agreement entered into by and between the landlord of the premises, and/or his/her/its agent, and "woman" and "man" as tenants.Anybody know?

I stumbled upon this article, written by a tax attorney, in a respected tax magazine https://www.thetaxadviser.com/...It implies that the 3-yr window on amending your tax returns and claiming a refund starts on the day you actually filed your initial return and NOT on the extended due date.

Between Covid delays for permitting, construction delays to keep bringing the inspector and engineer back in as we found more and more structural issues, then amending the plans and waiting on them to be approved by the city after each amendment, plus a GC I hired that lied about his level of experience and took forever to finish plus ignored every material selection I made and ran with his own finishes that were mostly bargain basement closeout garbage, it took a year and a half to get this from acquisition to stabilized. 

From my experience in NYC, you may need to amend the contract while your deal will progress and the attorney will handle it.