How could you set up a minimum wage so that it was adequate and reasonable and did not just cause businesses to go elsewhere?

Assume for the sake of argument that a minimum wage is a good idea. Assume there is a reasonable amount (a living wage) that people should be paid.

A living wage would be different in each area. San Francisco is vastly more expensive than Montana. The same minimum wage would either be too low in SF or too high in Montana.

And if the changes in minimum wage is dramatic between areas, business could just move across the line to pay less. Walmart for example built its stores outside of towns so it could get the customers from the towns without having to pay the taxes.

So how could you structure a minimum wage so that people were paid a fair amount everywhere but it was not easily bypassed by a short relocation?