There is a massive shortage of new bikes currently and has been for a while and is going to stay that way till the summer. Unfortunately that has pushed the price of used stuff up massively so people are digging out all sorts to sell while the prices are good. If you can avoid the older (once expensive 26" wheeled stuff) used bikes as the bits are getting difficult to get as the spares are running out and being manufactured less.
At 4'8" look for a small framed bike with 27.5" or 29" wheels and make sure the chain and cogs are in good condition as the price for replacement parts are currently at the highest they have been for along time
At 4'8" look for a small framed bike with 27.5" or 29" wheels and make sure the chain and cogs are in good condition as the price for replacement parts are currently at the highest they have been for along time