I actually used a Joint Sponsor for my greencard (that was approved) that was a combination of Social Security Retirement Income + Real Estate assets on a second property they had. I-864's themselves according to my USCIS officer when I went to the interview are decided if they're qualifed or at the National Benefits Center before getting sent out to the local USCIS offices in each state.
I did get a RFE for it, I thankfully navigated it thanks to a lot of information a fellow user called @Family had posted over the years. I don't think they're around anymore but basically you'll want to be meticioulous with your information.
- Make sure you've sent your I-864 from your Sponsor alongside your Joint Sponsor's I-864. You need both to include tax returns and all supporting tax documents W-2's or whatever for the Primary Sponsor and then a SSA-1099 for your Joint Sponsor showing previous years. Make sure they are spotless.
- Detail Income via 12 monthly deposits showing income paid into the account from their SSA retirement checks alongside the yearly letter you get from the SSA detailing how much you get per month.
- You can use a property tax statement showing value of the property, It's what I used to show value in the property. The property was also free and clear but never had a mortgage so I made a statement saying that the property never had a mortgage.
- You will want to also include a letter exactly detailing WHY & HOW you qualify. You want to make it as simple as possible for the USCIS officer reviewing it to understand. As a brief example you'll want it to be like this
- Joint Sponsor's Yearly income is $X (See Letter from SSA, See 12 months bank Deposit statements)
- The Value of the Property Being Used is $X (See Property Tax statement, Refrence to where value is on the letter)
- The Requirements to qualify is Your Household Size listed on the I-864P
- Income requirement minus How much your Joint-Sponsor earned
- Take the Remaining income required x 5 and then compare that to the Asset value saying you more then meet the requirement to qualify
Bare In mind this was a value on a second home and this is for Adjustment of Status just incase anyone other then the intented recipient is reading but Assets can be used if they're done correctly.