An honest rule
of thumb - is that any boat repair anticipated is likely to take at least 3 times as long as expected, and cost at least 3 times as much as expected. Opening up one repair usually leads to - at least - one more that was not previously known. Sometimes 5 or 6...
It's great that you have the ambition to take on a project boat, but trust anyone who has actually done it - almost ANY used boat
is a project boat.
Find something in the best condition possible for what you can afford, and plan on spending at least the purchase price
over again in repairs
and refurbishment. They all need work, but anything with rotted deck laminates, completely trashed out cabins, repeatedly patched up electrical systems, or rusted steel hulls is a HUGE project. HUGE. Almost a black hole of work. It can be done, no doubt, but it is a LOT of work, especially for someone with no specific experience.
There are a lot of boats on the market, but I'd leave the bottom 1/3 of the used boat
market alone - if you actually want to finish the repairs
, and still have any money, time and inclination left to sail it in the next 3 years. Don't start at the bottom of the market and work up - start at the middle of the used boat market and work up. Those are truly the best bargains, money and time wise, in most cases. Refurbishing a used boat and implementing your own custom ideas is a great experience, but you really need to start with something that is not just a black hole of problems.
Good luck & check out some of the specific used boats others have mentioned in this and other threads.