it may not be a lucrative business as not many people are into crypto. and most crypto users are using online exchanges to convert their crypto to fiat like binance and kucoin. but in-person retail store or shop will come in handy to some people who wanted their cash straight from crypto. because in online exchanges, to get your cash on hand, usually you convert your crypto to fiat, then with p2p, you send your fiat to your bank account or online wallet app and then withdraw it to your ATM.
expect that the business may not be busy as compared to other businesses, as right now, only few people may have their interest to crypto. but if it is already in front of them, they may try getting hands on crypto, who knows?