I run both MyNode and Umbrel on 4GB RAM Ras Pis. I have no idea if my ISP is ok with the bandwidth but I haven't noticed any spikes in the price of my bill or anything.

I think exchange hot wallets would be a great idea. There are also some TxIDs here on https://kycp.org/. You might be able to get some good address ideas from that list.

Keep it up.