It really depends what is playable for YOU.
If it should be really well playable there is no cheap EUB.
If you want to learn how to hold a double bass, stay away from tripod mounted EUBs.
The cheapest more or less acceptable EUB for me is the Stagg, but manufacturing quality differs a lot and you may need to change some things to get it well. Also the model with the rosewood fingerboard is better. The body separator (to be able to ress the instrument against your body like an acoustic double bass) is weak and could be made better. Keep in mind that this is a beginner instrument or an instrument that will only be played occasionally. You may want to get a better instrument after some time, but this one would cost about two or three times the price of a Stagg. It is good to find out if you would like to learn double bass, but a real double bass is better and cheap double basses are not much more expensive.
And you need lessons. At least for a year, I think.
Technique differs a lot in plucking, lower and upper positions and you can hurt your body if you do things the wrong way. You also ned a lot of practice to get your intonation right (maybe a bit less if you also play fretless). And you should also learn to play with the bow. With the bow you hear your intonation better to be able to correct it when needed.
