Yes, put another SIM in the old phone.
I'm guessing you are in the USA (as a Verizon customer). Most on this forum are in the UK so not too familiar with what deals are available in USA.
In the UK (and the rest of the world as far as I know) all phones are SIM based (unlike the US) and so is a very competitive SIM market. Vast range of pay as you go SIMs are available free and just need to purchase a basic top-up (ideally that never expires as long as you don't use all the credit - although with most you do need to make at least on call every 6 months or so to keep the SIM active). Maybe see if you can find something similar (or better) in your neck of the woods.
Having said all that, have you actually tried using the old phone on WiFi without a SIM?