@douglindag Welcome to the BassBuzz forum! When you have time, join us on the Introduce Yourself! thread.
You can look here for an idea of what is out there.
Guitar Center - Used Fender Bass
There are multiple web sites that sell basses. For a bigger selection you can search Google for “used fender bass”.
Keep in mind, there are additional costs when buying a bass.
$50+ for a setup
This is pretty important and can make a big difference to how your bass plays and sounds. Spending more money after buying a bass might be frustrating but this puts your instrument in prime shape. Do you have to get a setup? No, but in the long run you want one. Part of this is knowing what your bass is supposed to sound and feel like so that you know the difference if something is wrong.
$20+ new strings (if needed)
Probably included with your setup. Do you have to get new strings? No, but if you’re buying used, it gives you a chance get rid of somebody else’s funk so you can start off with your own funk. Just to be clear, I’m talking about the literal funk and nastiness that accumulates in strings.
$30+ a “good” bass guitar strap
My cheap bass strap cuts off the circulation to my arm. Do you have to get a good strap? No, a lot depends on your general health. A bad strap can be painful and a good strap can be… relaxing. YMMV.
$30+ a tuner that handles bass well
Not all tuners handle the low tones very well and that can make tuning frustrating. Do you need an expensive tuner? No, I use a very cheap tuner. It works but it can be annoying and I have considered throwing it off the back porch or stomping the guts out of it, just to watch it die.
Also, you’ll need an amplifier but that’s a whole separate conversation.
As to playing melodies, this video gets into that and there are links at the end of the post to melodic sheet music for bass… and you’ll get to see Bass Bot.
How to Learn Bass Scales (Become a Better Bassist, Not a Robot)
Good luck and if you have any other questions, don’t hesitate to ask. 
Edit: @Gio beat me to it on the video.