Nothing wrong with picking up a used tripod but if you're serious about using it spend a little more and buy something that's quality. I've owned cheap tripods in the past and I missed photographs because of them.
I have several tripods some heavy, some light, depends on how much weight you're wanting them to support and how far you have to carry them.
Have a Gitzo safari sport which is the heaviest, don't use it unless I'm shooting with long glass or the tripod is going to be in water. It has reversed legs which makes it perfect for that.
Have a couple Bogen tripods, don't remember the model number, that I used a lot when I shot medium format. They were much lighter than the Gitzo. Pretty good tripods as long as you remembered to keep the locking mechanism tightened up. I always carried a wrench with me.
Currently I use a compact Benro carbon fiber tripod, which I really like. Light, easy to set up, will support most of my stuff pretty well. It's probably a little light for a big, fast, telephoto lens.
Also remember, the best tripod with a crap head isn't going to work well at all. You can find those used as well.