Welcome to the forum, Scott!
That 148C is a nice looking machine but at 530 lbs. it would be a ball buster to move. $250 is probably not a bad price but I would offer less because machines that size are not as desireable due to the size and weight. Keep in mind, if you do a quality paint job you will have more money in that machine that it will be worth.
That being said, if it is working and you are looking for a good garage machine, offer the guy $150 and see if he bites. Otherwise, I would keep searching. There are a lot of good machines out there that are not as big and heavy!
Tim