Question : How many visitors per month should I have to do ads?

About how many visitors per month should I have so it makes sense to do ads on my site?

I built a baseball site.  Its recently been on ESPN.com, Yahoo, and some other big sites... so I'm getting some good traffic now.

I have zero experience with online ads. I assume I'll go with Google's ads. I'll take other recommendations if you have them.

Right now the site gets about 50,000 steady unique visitors per month. That should grow quite a bit in the coming months, and there are days when it gets flooded from big links.

The nice thing is the site is very niche (baseball). As well, visitors are very sticky (they tend to visit a ton of pages because each baseball season is cataloged on a different page, etc.)

With that in mind... at what point, in terms of numbers of visitors, does it make sense to put ads on a site.

I don't want to do it if it means like $10/month in revenue. But I also don't need it to be thousands of dollars in monthly revenue.

Answer : How many visitors per month should I have to do ads?

This is something that is very hard to estimate in any specific case as results fluctuate significantly based on diverse factors.  Take any numbers you read with a grain of salt.

2%-4% CTR per impression (page impression, not ad unit impression) is pretty good on the whole.  Niche sites will do better than more general sites, because the ads will be more targeted.  Two BIG factors in CTR are placement of ads and quality of content, especially text content.  Also important - diversity of content.  Net savvy visitors tend to click less frequently.  And so on ...

So, to start with, take your monthly page impressions and x 2%.  Consider that your starting number of clicks/month.  CPC rates vary considerably, too, but for the sake of the estimate, $0.10 - $0.40 averages out to about $0.25, so multiply your clicks/month by $0.25.  If you have a good site with good traffic, you might start out around there and move upwards as you refine your approach.

Again, these are very rough estimates and actual results could vary considerably either way.