How do you evaluate a mixed property, residential + store ?

[Matt Liu]

A deal came my way that is a mixed property - 4 residential units plus 1 used furniture store on the ground level. I know how to evaluate residential units, but for the furniture store, my concern is that if they ever leave, I will not know how to fill the unit again. How might I do due diligence on the financial stability and long-term tenancy-potential of this furniture business? Anything I should watch out for?
Thanks!