Unfortunately, this is where the "5 P's" rule comes into play. "Prior Planning Prevents Poor Performance."
I am working with a customer on the plans for a new retail building. While it's a small one - maybe 30 x 60 - the customer wants the possibility of later dividing it into two separate units. Knowing this 'up front,' it's relatively easy to do a lot of the groundwork now, at the start.
Converting an existing building is a major undertaking - especially if the original job was done in the simplest, cheapest manner possible. Remember: switch gear is custom made; if you don't ask for provisions to be made, the cabinet won't have what you need in it.
It MIGHT be possible to 'cheap out,' if the customer wants to have his own metering, and do his own billing. In that case, the customer can instal a meter at each panel. While E-Mon has made a business of this market, reconditioned PoCo meters are available for less than $50.
Even so, it won't be cheap. The breakers for the switchgear likely cost $300 each - and there may not be space. Again, it comes down to the original plan, and how relevant it is to today's needs.