I just found this Sprint MVNO and it sounds interesting for (possibly) parking and very low use.
For $20, the $20 covers 400 "units" @ $0.05 each -- a unit is one Voice Minute, one Text, or 1Mb data at $0.05 each. Any amount balance expires in 360 days (NOTE: NOT ONE YEAR, 360 Days).
They have a $10 plan, too -- $20 equates to 200 "units' @ $0.05 but the balance expires in 120 days.
I think that porting in is free.
Tello is probably a better deal for parking and very low use -- the balance never expires as long as you use the device every 6 months.
$5 pay as you go credit gets you started, free porting / activation. Better rates too: 3 cents per minute, 1 cent per text, 2 cents per MB.
In theory you could keep a phone parked there for 83 years on your initial $5, just making 2 calls a year to keep it "active." 
Or a little short of 250 years on your initial $5, just sending 1 text message (costing 1 cent) every 180 days.