7 days? Possible but depending on a few factors:
- the niche of the site
- the keywords you target
- the competitors you have
- the ROI you expect
- your budget
This is a very general question so I gave you a very generic reply.
In my experience, the only way to rank a site #1 in 7 days in 2017 (cause it was a lot easier in 2012) can be done only if:
- you really chose a niche that's got a high ROI and really weak competition
- you invested at least 1-2 weeks in good keyword research
- your site is built on an expired domain and the on-page seo is spot on
So, can you do it? Possibly.
Is it worth it? Depends on what you want to get from it
Does it take 7 days? ABSOLUTELY NOT - the preparation before you launch the site is going to take you at least 2 weeks if you truly want to rank #1 in 7 days time from the moment you launched the site.