I've been doing SEO for nearly 20 years now (about as long as that's possible), built 3 of my own successful businesses from it, and run a 12-member agency in Chicago these days.

Here's my take.

You mentioned a lot of great tools there, but keep two things in mind.

- These tools tend to overlap like crazy, but they're all mediocre at just about all but one thing. That's if you're lucky.
- Having a system to use a tool is infinitely more valuable than the tool itself. Tools alone are worthless.

This said, here's a basic SEO tech stack that I'd consider:

- Ahrefs: they have the largest backlink database and a great web interface. Though, they also have the worst API by a lot (Majestic wins that).
- SEMrush: they have the best scrape database of Google search results.
- Screaming Frog: the best tool that I've seen to crawl your own site (by far). Somewhat of a learning curve, but pays dividends once you get good with it.
- Moz: Mostly just for their keyword explorer, which is quite good. Tracking MozCast is nice too, though that's free.
- BuzzStream: The most impressive outreach CRM that I've encountered.
- Linkdex: for really intense per-keyword proposals.

That's a strong core and how to use it.

Best of luck.

Do inbound marketing.

Or, outbound/direct marketing.

Those are basically your options. :)

Since your question is so broad, it's tough to be more helpful than that. But as square one, I'd define a narrower beachhead market. Web design, development, and SEO are huge disciplines, each with many smaller disciplines beneath them, and quirks for various markets beneath that.

Currently, based on searching LinkedIn for companies that also offer that stuff independent of geography, you have 10's of millions of competitors. By refining to be more niche, you could easily lower that to 10's, which is usually a great, early move for any business. It can always grow more broad later.

Have you seen The Social Network? :)

I've seen maybe a dozen companies with many partners utterly melt-down. One of which I was a part of.

This is something you'll largely need to answer for yourself. Everybody thinks their situation is different, but where partners are concerned, greed always seems to rear its ugly head somewhere, in some way you never expected.

My advice is to have a strong operating agreement, that nails down what to do if somebody goes and blows all the company's money at the club or other (soundingly insane, but) real things that happen. Also, the more obvious stuff that's usually covered by your attorney and a boilerplate doc - tie-breaking votes, voting when someone's unavailable, etc.