You should be able to get a decent, in tune, piano for about 800. After that it's up to yourself. If your mother plays piano she may have her own views about what is suitable, also what would match her decor etc. Without getting too technical most pianos have a life of about 100 years so, after that they become very difficult to tune. Best to get one not more than about 60 years. You can often pick up free pianos but unless you know what you're doing and can get hold of a piano tuner you may end up with a landfill item. Marie's antiques in straffan sell re-conditioned pianos (not connected to them but like to go there to try them out !) and have knowledgeable staff. Worth going for a look and some info. Otherwise find someone who knows about pianos to look at anything you are considering buying.