Would you keep a tenant when buying a property?

[Matt Slease]

Looking at a property with a tenant already in place, has been there for 8 years.  They're paying $700/month currently, market rent looks more like $900-950, possible more if it's fixed up nicer.

Would you consider keeping the tenant?  

Cash flow doesn't really work at the current rent, but would it be smart to say this is what the new rent will be if you want to stay?