Something like supporting multiply operating systems also would cost a team of 2 a lot of time due to basic things.
You would need to test on all platforms, regularly. You would need to be able to debug on all platforms (setting up your ide multiply times). Your bug report has to be more precise.
You also need to either fully use an technology which in theory supports all platforms out of the box OR you would need to develop everything with either multiplatfrom libs or abstract it away and use different implementations underneath.
Alone accessing a file is different on all three OSes.
The best way for a very small team is to make it on Windows and just pay someone to migrate it later if it is already successful enough.
You would need to test on all platforms, regularly. You would need to be able to debug on all platforms (setting up your ide multiply times). Your bug report has to be more precise.
You also need to either fully use an technology which in theory supports all platforms out of the box OR you would need to develop everything with either multiplatfrom libs or abstract it away and use different implementations underneath.
Alone accessing a file is different on all three OSes.
The best way for a very small team is to make it on Windows and just pay someone to migrate it later if it is already successful enough.