That's hard to say, without knowing the condition, outside of the missing wheel, which is probably why it's been sitting. Part of the equation will be be how much it's going to cost you to replace the wheel. Also, if the wheel is missing, you're going to want to make sure the frok and/or frame isn't bent. Beg or borrow a 700C front wheel to take with you, so you can check it properly and take it for a test ride.