Of course there are always exceptions based on the creativity and vision of the site owner and their team, but usually it takes about a year to get going good with a new site, new domain.
If you work really hard, optimize your site as best you can, add content or update the site regularly and build back links you can expect to be making some good money in about 9-12 months.
I know sites that have totally blown those numbers away, but it doesnt happen that often especially in your industry. It is mainly due to the industry professionals that tried to cheat the system in the past causing more filters and rules for the ones now.
On average, if you work and study hard you can make a great living in this industry and on the Net. Be creative and think “outside the box.”