I don't have a land-line. I have an old cordless phone laying around that I used to use with a service called Magicjack where you have a USB device connected to your computer and the cost was originally $99 for 5 years. Currently that is running out and I think the price is now $120 for 5 years but I'm not going to renew because I use my cell phone and the issue of running over the minutes is no longer an issue because I don't run my own business or do independent contracting anymore so I don't make or receive phone calls for business purposes anymore.
If you don't need data roaming outside of the Sprint network, you can use a service called Ting. It is super cheap. $6 to be connected to the service and you don't lock yourself in a set plan. Say you talk for 90 minutes, send/receive 90 texts, and use 90 megabytes of data, the cost is $15 plus the government fees and taxes(which is just under $5 usually), so $20 when it is all said and done(with very low usage). If you use a little more the costs aren't too bad.
https://ting.com/rates
Since there is no contract, the phone isn't subsidized so you pay full price for a phone but they have a list of Sprint phones that can be used with Ting and you can usually buy a phone that is a year or two old from someone who swaps phones often for a low price. I bought a used Sprint Android phone off their compatibility list for $50.