Wow! How long is a piece of string?
Well, assuming you are not a troll.....Okay, the budget is a tight for a bluewater boat that size, so TLC will definitely be needed - and a lot of time. It would be tough to get a working 100' sailboat with that budget, and if you did, you would need to hire a crew. If you are thinking about girlfriend and small family, look in the 40'-50' range.
The bigger the boat, the greater the cost - generally exponentially. A 100' sailboat is generally millionaire class. Where would you dock it? Slip fees? Refuel fees? Imagine what a new sail would cost in a boat that size. Think also of the parts, the cost of refurbishment. Think of ongoing maintenance. Haulout fees. Etc etc.
So many of your questions are very subjective, but there are many experts on this forum. The more specific the questions, the better answers you will get. And my opinions are worth what you paid for them!
Single versus twin mast - in a boat that size, a single mast is very big (in a 100'sailboat - enormous). Big means more difficult to handle, exponentially more expensive. Twin masts are generally less efficient, but easier to manage. Friend of mine has a 54', all electric winches, single mast...almost sailable single-handed. Needed TLC but bought for around $250K. Probably put in another $100-200K sorting it out. And the annual maintenance - oh, my, more than my boat is worth every year.
Hull type - depends largely on your expertise. The owners of each generally love their hull - woodies would never go back! If you are a skilled carpenter, a woody is an option. Otherwise, probably not. And for an older boat needing TLC, I would suggest that wood has the highest hull risk, followed by steel. Plastic tends to cope with neglect better.
Others may chip in with ideas; in the meantime you may want to look at Bumfuzzle
- a funky family who sailed for a few years in a catamaran, then toured around in a VW van, finally bought a 43' monohull needing TLC - and live on it with two children.