If you want to start bass from fretless I suggest you a lined fretless, expecially if it is your first bass so that you will have less problems with intonation. These days not only beginners but many experienced fretless players go lined fretless too (like Jaco and Gary Willis just to name two

). I think that intonating an unlined when playing in the higher register is an almost impossible mission, expecially when playing fast.