Sell Orders

It all depends on what you want to do in a rented system, how many persons are in that corp etc, that sets your budget.
We've got 1b system rented for 20-30 duders since they can upgrade that system and mine their asses of in mining anomalies, we've got 10b systems rented to solo guys because they want the system all to themselves so they can rat with 5-7 carriers using iso boxer or something. We've got 1b systems rented to 1-2 guys that want to run a reaction farm, we've got moons rented to them just to make it easier for them to get isk.

It all depends on what the renter wants. As you can see from this thread we don't get many complaints as we're reasonable and not asses with renters, hence the alliance growing so fast after the war was over.
The biggest group of renters are either pve alts from alliances that want to ratt/min in peace, or corps composed of players that want to take the game easy and play casual, often IRL friends.