alot of people have tried this. but here is the experiences of them.
1. in countries that deem bitcoin as a legal currency.
by accepting fiat in exchange for another currency as a business, those 'agents' become MSB's(money service businesses). which require licences, regulated insurance(X reserves locked up) and inspection/auditing/ costs.
.. however there are some countries that have not determined bitcoin as being a 'currency' by law, by which that means that bitcoin is treated as simply an asset(product/service) and thus agents in those countries are thought of as just merchants.
so be aware of the legal frame work the businesses have to work within when setting up in certain countries
2. the costs of opening a business are not cheap, nor are employee's. so while wanting to fight the 'remittance fee' of places like western union. many of these start-ups end up realising the hard way that they have their own costs to cover, and so they start charging a fee.. in many cases they pretend they dont charge a fee, and instead just adjust the 'spread' of the market price to hide any suggestion of a fee while scalping a profit from the market spread. either way it ends up that the customers at both ends of a remitting see a noticeable difference between how much was sent and how much was received compared to forex exchange rates.
so keep in mind of costs associated with running a business. even if you can avoid the countries that require legal costs of regulation of MSB, you still have the employee salary, and the volatility swings which usually add on a few % of difference to the market 'spread' on both sides to cover both employee's(no one works for free)
3. what ends up happening, especially in countries that deem bitcoin as currency (MSB licence costs associated) is that instead of there being independent small businesses in each town of a country where each business has to pay a licence fee each. they all end up centralising into a national/international company where the company buys a licence and the workers in each town just act as employee's of the company.
4. for the countries that do require MSB licences. its not just the licence application fee. its the ongoing monitoring/supervision.
lets use numbers from america. page 2
money transmitters might be monitored for 140-500 hours a year at $107 per hour cost, which is ~ $15k-$54k dependant on volume transfered
other upfront costs are included aswell like staking(collateral locked) of certain amount of fiat/crypto reserves, where amounts locked are dependant on how much volume shall be done in a year.