You can feed one as a subpanel if you like, but you'll need to pull a new 4 conductor (2 line, 1 neutral, 1 ground) and feed that from a double-pole breaker on the main panel. You then rewire the (now) subpanel to isolate all the grounds and neutrals from each other.
What you save is the meter/hookup fee every month. That's around $12/mo here. What you give up is the current cash needed to make the changeover, the future flexibility to lease out part of the building to another user or potentially to sell them separately down the road, and the ability to account for one of the uses differently (if one use is fully deductible and the other isn't, for example, you could fall back on per-sq-ft allocation, but that might be less advantageous if the deductible use is higher/sqft).
I'd probably skip on doing the work; the ROI is definitely poor if you have to pay someone to do it and pay a permitting fee (which you probably can't avoid if required in your area, since the utility will know about it). If you can DIY all of it (and are willing to research and teach yourself how to do it safely as a few details aren't obvious to the inexperienced), the breakeven is probably still pretty long (and you've given up some future flexibility).
