You make lots of gold raiding but a private guild just for your boxing team wont make you much gold. You'll make enough to cover guild repair for your teams but you wont make a lot.

Once level 25 you can sell your guild and make a lot. Not sure what guilds go for now but they used to sell for 100k+ and I have seen forum posts about them selling for 250k.

As for the amount of time it takes to get to level 25, not long at all with a 10 man team. Raise your team to 90 and a few dailies and you'll be there.