If you're just getting into hand work, it's probably best to avoid secondhand saws. They will almost certainly be blunt, and quite possibly bent as well. Later, as you develop, you may enjoy the challenge of refurbishing old saws, and that could eventually give you some exceptionally good tools. However, it's better to learn how to saw before learning saw sharpening.
With that in mind, there are several options. It may be worth buying a hardpoint backsaw from one of the sheds as a first saw. Reasons - it'll be pretty cheap compared to new 'nice' saws, but more importantly it'll be straight and sharp, and will keep it's sharpness for a fair while. Try to find one with a fairly heavy back if you can; the weight helps the saw do the work. Handles are a matter of personal taste, but find a comfortable one. Thus, you can concentrate on developing sawing skills knowing that the tool is adequate, if not all that aesthetically pleasing.
Later, if you wish, you can supplement the kit with some nicer saws, new or vintage (for refurbishment). Most people tend to have a small one for dovetails, and maybe one or two larger ones for cross-cutting on the bench and for tenon cheeks. (Some people accumulate far more than that, though - beware! Saving neglected vintage saws can become addictive....)
