If it is a hose, shouldn't be a big problem to replace. If it is a heater core under the dash that heater hoses connect to, that's a bigger problem, often difficult to access. If coolant is leaking from the engine and not a hose, I would shy away from it, too many possibilities there, like a head gasket failure, water pump-coolant will be leaking from front of engine then.
It would be best if someone accompanies you who has worked on cars to help you decide. Look it over carefully, test drive for a bit until engine reaches normal operating temperature, monitor the temperature gauge, drive at freeway speeds with engine warmed up-then you can make an informed decision. Good luck.

I would have a mechanic look it over. If a heater hose is leaking it is a simple fix. But then why don't the current owner fix it ?
Could be something serious like a leaking head gasket or heater core.