Benefits vary based on income, but they're heavily weighted toward the low end. So, a poorer person will get lower benefits, but their benefits will be a greater percentage of their income.
Doing a fast calculation, someone who earned $25k (this year, not every year with prior years taking into account how earnings change) would probably get about $14k/yr in social security. So, it isn't a huge amount of money, but it would bring it up.
it's worth noting that $25k pretax (and note $25k seems to have been a high), even at a modest tax rate, could easily fall (post income, fica, etc) to $18k post tax. Or $1500/mo.
medicare should start shortly after the 65th birthday, but people still have to buy Part B and either part C or D. afaik part B requires a typical 20% contribution; this can be quite painful if you're living / attempting to maintain a house on $1500/month
old age is no picnic, particularly in the usa, and that goes double for people who don't have significant savings