He's a CPA with a focus on strategic tax planning.

Because of the nature of a tax lien, it would be difficult to obtain financing from a commercial lender secured by the tax lien itself.  

You will want to fully understand the tax reporting burden you will face. 

There may be a property tax benefit to leaving pieces.

The problem is that we need to be careful with the word "passive" because it has a very specific meaning in the tax law, and it is not intuitive.For example, losses from rental properties are usually passive but not always, there are some exceptions.

Joint tax return?  

Is it allowed to purchase a property with our primary home that has a detached ADU on the same tax lot.

@Frank FloresInvesting in delinquent tax sales in Houston can be profitable, but it comes with risks.

Ideally this would be done after doing proper diligence and making sure that the sponsor's skill and expertise matches the opportunity being presented.  

You are converting their tax free gain in to a taxable gain.