The only annuity which should be considered is the
fixed SPIA - Single Premium Immediate Annuity, with a built in inflation adjustment.
Not saying all SPIAs are a good deal - there are certainly some bad ones. But they are the ones where you can actually find a good deal, especially for an older person who just wants to guarantee income.
The basic tradeoff is that you are giving up the possibility that you(your mother) will leave a residual (more money) for your (her) heirs. The upside is that the annuity company can therefore offer you a higher monthly payout than any other guaranteed fixed income investment (bonds, CDs, etc).
I Googled up an article for you:
https://obliviousinvestor.com/single-premium-immediate-annuity/You obviously would need to get quotes from a variety of different companies, ones that you are reasonably sure will be around. I did some quick online quotes, and it seems a lot easier to find non-inflation-adjusted quotes. It looks like with NO inflation protection your mom could get around a 9% return (ie, if they put in $500k from the sale of the house, they would get $45k per year for life) - an inflation adjusted SPIA would start with a somewhat lower return.
Personally, I would start somewhere like Fidelity - they have discussion here:
https://www.fidelity.com/annuities/immediate-fixed-income-annuities/overview...and then hit a bunch of online brokers, etc.
So again:
SPIA
Fixed
Inflation adjusted (probably)