I am rarely home so I want to get the rock bottom rate. If I do use my home phone it would be for a local call.
It is just about impossible to get the phone bill for a wireline below about $18/month. Generally there are about $8 in various mandated charges like 911, and Federal Subscriber Line charges. Basic wireline service (measured zero) is about $10 a month in most markets as long as you don't buy inside line/wire maintenance.
The lowest cost is likely to be a prepaid cell phone plan. If you buy $100 credit, that will usually keep the plan alive for a year, or until you have gone through $100 in cell phone charges at the prepaid rate. If you rarely make or receive calls, the $100 may be more than a year of calls.
Verizon, AT&T and T-Mobile all offer similar prepaid plans, so if you live in an area with good wireless service, that may be attractive.