Is second hand scuba gear save as i need to buy a full set but i dont know how much should i pay and which make i should buy. Also are drysuits very dangerous for a teen ager as my son gets very cold he is very tall and is not stupid he has done some lessons and loved it

Buying second hand scuba equipment does have its risks.

You need to research it to see if the equipment is still being made. This is for when the gear needs any servicing (which is done annually).
If the items have been discontinued by the manufacturer for more than 7 years there is a good chance that replacement parts may not be available.

You also need to know when the gear was last serviced. Just because it has been sitting in someones closet, attic, basement or garage untouched for the last 5 years does not mean that it doesn’t need to be serviced. There are parts that need to be changed out annually.

Buying new is wiser as you know there are parts available come time for servicing. The equipment is backed by manufacturer warranties (for original owner when purchased from a manufacturer authorized dealer).

If you are buying new on the internet, always check to see if the website selling the gear is a manufacturer authorized dealer.
The dive store where I work sells in store as well as online.

We are also listed on the manufacturers websites as authorized dealers both in store and online for the products that we sell.

As far as drysuits, they are great for cold water diving but people wearing them need to be trained in water on their proper use. Dive Facilities will usually have a separate course for those wishing to use drysuits.

Manufacturer warranties are null and void for a person buying second hand scuba equipment.