Sand would make a nice short-term profit, but the only area where sand mining is unrestricted is in the territory of MtA. The deserts are already in a pretty shitty state, so it's not unthinkable that if their state deteriorates there might be anti-sandmining laws set up in MA.

However, sand mining has been a nice way to activate newfriends. I'd argue it was a major contributor to the population boom last summer. During the summer we had some Nexicans set up a facility in the southern desert with sell chests for sand and free golden shovels. Newfriends could go there, dig up some sand, and sell it for pretty nice prices. There's always demand for sand since it's needed for making bottles for XP.

I'd personally recommend going into wood business, as it would have a minimal environmental impact on the region. It's sustainable and you could use the same concept as the sand facility did; provide free golden tools and set up sellchests for wood where people can exchange their wood for iron. You obviously won't be raking in as much dosh but it will take minimal effort from you and would provide jobs for newfriends to help them get started. It's something I have wanted to do for a while but haven't been able to due to my absence. You could also take advanage of the deserts to farm acacia.

Regarding cow (and pig) breeding, there's something shwonky going on with mustercull that's fucking up breeding, so you might want to avoid it for the time being.

Courier services are something that I'd recommend due to our central location and portal access.

A plain ol' trading company in MA would be really cool. Buy 'n' sell, make profit when possible. Also feasible thanks to our location, and would provide a larger range of goods for sale in MA.

If you are only after copious amounts of diamonds (boooorriing) go mining and find yourself a vein. Silk touch + ore smelter = $$$. There's way more interesting ways to get weathy in civcraft though, so I'd advise against this.

If anything, I really hope you come up with a business that can employ newfriends in some way.