Cheap/free way to have a dedicated work (land) line?

I've been given the ability to work from home, but they strongly recommend that I use a dedicated land line as my 'work number'. I really think it's unnecessary, as they simply just think that it will be more reliable and stable than a cell phone, but I hardly have any issue with my cell phone (especially if I'm just going to be sitting in my home office and using it).

I do have an existing land line (that I share with my family), but they suggested I get a dedicated line in case that one is being occupied. During business hours, no one will really be using the land line (or even at home), so I think I can manage with one.

My current solution is using my google voice number that I have. I can make that forward calls to both my cell phone and my land line, so, in the event my land line is being used, it will be forwarded to my cell phone. I was wondering if there were other alternatives I could look in to (internet land lines, etc).

Thanks in advance.

(Also, I realize adding a second land line is probably fairly cheap and worth the trouble for me, but I'm on a tight budget and, if I can get around it, that would be preferable).