Don’t buy a VPS solely for STORJ. It will most likely not be profitable. Only use unused storage space an a server you use for other things too.
May I ask how much you pay for a VPS? And how much storage does it have?
Edit: Found this post How much can I earn with a 1GBit connection?
Now I can tell you it will never be profitable. Without surge payment I would have earned less than $22 for 4.5TB actual stored (not assigned) data. You pay $21 alone for a VPS with 2x2TB (I guess in RAID1). You might make a small “profit” if customers start downloading their data a lot. But even then it will take month to fill this space where you make a loss…