I use a pay per head software, so the vig usually is enough to cover the pay per head fees. Then I just saved up a certain amount to cover for possible expenses (if I would be short in releasing payouts). Minus bonuses for new players, around three weeks. Would have been sooner, but I really wanted to have that extra budget there saved up for a rainy day.

Then after that I would take out a tiny bit from my weekly revenue to increase that amount. I do that because as the months went by I started dealing with more volume, and I needed to match that. If you want to save up for that amount up front to keep all future revenue as profit, then go for a large amount- might take you a few weeks or maybe a month more to start seeing that ROI.

Increasing betting volume is a crucial strategy for improving Return on Investment (ROI) in a bookie business. It leads to higher gross revenue because the more bets placed, the more money flowing through your sportsbook. In addition, more volume means higher gross revenue due to the fixed house edge.

Higher volume also means you get more data to refine your odds-setting process. The more accurate odds you offer, the more consistent profits you earn over time. 

You can read this tutorial, https://priceperplayer.com/how-to-increase-the-sports-betting-volume-in-your-sportsbook/, to learn how you can improve the betting volume in your sportsbook.