If he's on 6 figures, and she looking for work, so income isn't a problem ... why not just rent it to them for 6-12 months (or so) AT MARKET RATES for them to build up a deposit and get some employment history - and separately - both parties sign a contract giving them first right of option/refusal to buy AT MARKET RATE at the end of that period.
Saves a whole lot of headaches and means you're not bound by an old price, if the market moves up.
Also means if they like it, they can buy - if they don't like it, they can move on without skin of anyone's nose.