
You can try your son's Soloflex
and see if it is comfortable and challenging for you. If he has the free weight
attachments, that would be very useful. It may help to check out their web site before you get started.
If the Soloflex is not comfortable
for you, I would recommend investing in free weights. (Your son may have some
dumbbells around as well.) Dumbbells can be purchased for as little as $0.50 per
pound at discount stores or you could try finding them used. Second Hand (Play
It Again) Sporting Good Stores often have great bargains.