Aloha.It is possible to buy a telescopefor under a 100 dollars,but to be honest my friend you wont get much for your money.Dont be discouraged however.If your son is into Astronomy and you guys are just starting out it may be agood idea to start of with a good pair of binoculars.A simple 10x50 are a good start and will help you find your way around the night sky.They have a wide angle view so you will get to see alot more when you look through them.It can be a daunting task trying to find your way around the night sky if you are not so familiar with where you should be looking.Be patient! even if it takes several years save up for a good scope.It will be a worth while investment.The sky is not going anywhere,not at least for the next few billion years anyway.Get a sky chart,go outside and enjoy your new hobby with your son.He will thank you for it in years to come.When you do have a bit of cash to spare there are many good telescopes you could pick up for about 500 to 600 dollars.Try perhaps Skywatcher.Anything from 6" upwards will give you something worth looking at. Hope i could be of help to you.Clear skys buddie.:glasses1: