From experience of what you found out 'after' you bought yours, what are some things to look for that you normally would not be aware of, when shopping for a used sailboat?
With all due respect this question shows someone who is clueless about boats and what they want and what they need.
What any member on SN wants, needs, and would or have looked for in a new to them boat is completely irrelevant to YOU/
Of course you don't know what you don't know. Everyone faces this problem. But each person is in a different place in life.
It's self evident that an older boat, even well maintained is going to have more expense in terms of service, maintenance and needed refits/upgrades... especially if it has been normally used. Unlikely to find a used boat all tricked out to what you want and need that is in bristol condition and rarely used
You definitely need to figure out your financial situation to drive your choices, purchase and refits/upgrades. No one can give you much advice on this. Some are conservative and risk aversion... others the reverse.
Look at the reputation and various owner's comments about the boat you are interested. Take everything with a grain of salt.
And then you need skills to tackle the work on your boat... or pay for someone else to do it and hopefully understand what they are doing and charging and so on.
If you see a boat that you can afford going it, get a surveyor and have any closing subject to surveyor's findings. Tell the surveyor what sort of sailing you intend to do.
Go back and do your homework.