Please share with me some realistic standards

Let's say you got a person, who's done their research, has picked out a profitable niche, knows decent SEO to get their site ranked, etc... And they're using all avenues to monetize their site, Bing Ads, Affiliate products, etc...

Realistically, what can they expect income-wise? And how long will it take to even make their 1st dollar?

There is no right answer to these questions. It depends. If you're selling homes it'll take more time than if you're selling Fiverr gigs.

It also depends on how much you invest. If you can buy tons of traffic off Facebook and Adwords, then you may as well start making money on the very same day.

It is impossible to say.
Seriously, too many factors to be taken inconsideration.

Some people will hit big money straight away, others will struggle for years.

If you are exceptional then you could start earning tomorrow and have no limits on your potential earnings. Few people are that exceptional though.

I know people that started making money from the jump and some who still don't earn above $6k a month after three years of hardwork.

Creativity + research + consistent intelligent execution + reflection = success.