If you're not very experienced, particularly with fretless, I'd suggest that you first buy a cheap (Squier,say) fretted bass , and get to like it. If you need the c string, you'll particularly like playing two octave scales with one shift, it's really convenient.
Then take the frets out, fill them with what you wish and get it to a good luthier , e.g. a double bass person, to get the fingerboard dressed properly. The time you get acclimated to the fingerboard and instrument will pay dividends when you start working on intonation. At which time, that one shift will make more sense.
A properly shaped fingerboard is essential for a decent fretless instrument, and you'll have less than $500 into it.
Then take the frets out, fill them with what you wish and get it to a good luthier , e.g. a double bass person, to get the fingerboard dressed properly. The time you get acclimated to the fingerboard and instrument will pay dividends when you start working on intonation. At which time, that one shift will make more sense.
A properly shaped fingerboard is essential for a decent fretless instrument, and you'll have less than $500 into it.