If you run with Raspberry Pis, you still need a static IP for each masternode.  Check with your ISP on the cost.  Usually, one static IP is more expensive than a VPS, but a block of 5 will be a better deal.  I would also suggest running an i5 or i7 with virtual machines for multiple masternodes.  Cheaper than getting several Raspberry Pis.  Raspberry Pis are fun to play with, especially if you want to add temperature or switch sensing to them.  I have one that texts me when the mailbox door opens and runs cgminer to control some USB miners.

Careful with the lowend offers.  I tried to go cheap($1/mo) and had to ditch it. They would stop the dash process after an hour.  You really only need 256MB of ram and 5GB of space which should be easy to find for around $5/mo.