My husband leases office space in a business strip center. The 30 year old heater needs $3400 repairs or $6000 to replace. Who pays for this.. my husband or the landlord? Why would a tenant pay $6000 to replace the heater when he just has 2 year left on the lease... seems he would be buying a new heater for the landlord? So who pays?

There are very few laws for commercial leases. The situation is almost completely controlled by the terms of the lease. You have to carefully read all of the lease to find out who will be responsible. Pay particular attention to anything in there concerning who is responsible for general repairs.