I have 2 sites. 1 is already doing quite well and is on page 1 on google for most keywords. The other needs a bit more work. The niches are not insanely competitive but I need some simple work done to get them bumped higher which would be more the new site than the one already ranked highly. PM me if you can do this. I WILL NOT pay fully upfront as I have been burnt before.
Your goal can be achieved, but will depend on purely competition level and competitors for particular keywords which you are targeting. Interested to do the job [Experienced].
For me, this will give you a big loss, because when ever you will start with SEO you to done your work with one person