If you want a cheap older car a Volvo is probably not a good choice. Yes, you can find cheap old Volvos, but they will be in pretty rough shape. The ones in good condition have a higher price tag. Now, the good part is that a lot of the problems with the old 240 series is their interiors fall apart. The seats are worn out, the interior plastic gets brittle and breaks, but the motor and transmission and body are all still solid. If you don’t mind a ratty looking interior, you might find a cheap but reliable old Volvo. But you have to ask yourself, if the previous owners didn’t keep the interior up, did they do the oil changes and other routine maintenance? So, it’s a crap shoot.
The only other good news is that you can generally find parts for 20 year old Volvos. The local junk yards around me generally sell old Volvo parts as soon as they come in, but things like tail light assemblies and mechanical parts are available from reproduction sources as well as Volvo themselves. I have found the repro stuff is generally 1/2 the price of Volvo dealer sources. My daughter has an old 240 that runs well, but it needs the occasional part or repair. I’ve always been able to find the parts on line.
With all that said, if I were looking for cheap and reliable, I’d be looking at Crown Vics or similar “grandma” cars. Yes, they are big, but they have built that same basic car for 40 years. They are pretty darn reliable and every mechanic in the country knows how to work on them, and the parts are easy to get. You will get a much newer and nicer Crown Vic than any Volvo for whatever price.