About a site's Search Engine Optimization

I am about to do some freelance work just to test water.
And one of my potential client is a owner of a barber shop.

I can write him a website alright, but what happens after that I have no clue.
The thing I am worried about is that after I wrote him some site and host it online, whenever I search that particular site it does not come up in the search engine page. (or more like does not come up in the 1st few result)

I heard that a website needs some time before it can be seen on the search engine, because the search engine needs to index it.

If whatever site I put out does not come up into the 1st few search result, then it is hard to use it to promote your business isn’t it?
Also I will advise my client against SEM because it might cost him a lot of money, and also we are a local business, there is no point that everyone in china is gonna see his barber shop since most of people do not live in our city.
What do you guys think about SEM and does any one of your clients/former clients used it before?

I did some research on China’s SEM models. And all of them points out that as long as you keep paying the company(baidu) you will see they add in your site to the top of the search result and add a “ad” tag on it. So you will get more “clicks” but as soon as you stopped paying, your view counts decreases dramatically. It’s just a “pay to win” system.

How do I implement SEO into the site myself ? By including meaningful meta tags? Also baidu has a design/styling guide on their site (in chinese) as well as an article about SEO, if I just follow those guide line I should be fine right?