i did that for a bit years ago when localbitcoins were still trusted. it didn't earn a lot of money but it did earn some. here are some notes.
- you need to double check the fees the exchange is charging you. i was buying at that time at bitstamp. bitstamp did a shady thing with fees where they'd split your limit order to fill it, but for every partial fill they would round the fee up. so you ended up paying a lot more on fees than you should have.
- nowadays the lowest fee exchange for your buying is either binance or ftx.
- p2p markets to sell on are paxful, localcryptos, maybe localbitcoins (not recommended) and i believe binance runs a p2p as well. in monero thats localmonero and the only big exchange reliable with monero is bitfinex (binance reportedly freezes accounts who buy and withdraw monero)
you probably know this but for posterity: you need to have money in several platforms. you need to have bitcoin in the p2p platform so that people can initiate a buy from you. when they initiate a buy on the p2p platform, you already have to have fiat ready on binance or other exchange platform so that you can buy back the p2p trade at the same rate.
your risks: there is some fud around binance. i think that's probably fake. on the other hand, there is a lot of fud about tether (paolo ardoino of tether confirmed a few days back that legacy hedge funds are borrowing money to depeg tether). if tether gets depegged, all exchanges that list tons of derivatives denominated in tether will be in trouble. binance lists tons of usdt markets, ftx does not.
tldr; now is not the best time to do p2p arbitrage. you need calm waters for that. right now the markets are too volatile and there is a lot of risks involved in holding money on exchanges right now. i'd wait a few months to be honest.