You're already ahead of most SaaS founders I've worked with - that technical foundation alone usually eats up the first few months for everyone else.
One thing I'd gently push back on: starting with "finding the right keywords" is a bit old-school. Google's gotten way better at understanding topics holistically rather than matching individual terms. What actually works now is building topical authority around the core problem your product solves. Map out five or six topics your ideal customer actually worries about, then create content clusters around each. You'll end up ranking for far more queries than any keyword tool would ever show you.
For research, start with Ahrefs Webmaster Tools or Google Search Console - both free. Semrush has a free tier too. No need for expensive tools yet.
When hiring a freelancer, green flags are: they ask about your business model before they even mention keywords, they can show results from sites your own size (not enterprise case studies), and they talk about search intent and topics, not just search volumes. If someone hands you a list of 200 keywords sorted by volume and calls it a strategy, that's a red flag big enough to run from.
The biggest waste I see founders make is paying for a massive technical audit upfront. Most of it is just missing alt tags and broken images - stuff you can grab from Screaming Frog in 20 minutes yourself.
What actually moved the needle for a SaaS I was involved with not long ago was comparison and alternative content: "X vs Y" pages and "[competitor] alternatives". Lower search volume, but the intent is so strong those convert way better than generic blog posts. Start there, not with fluffy top-of-funnel stuff.
And please avoid the retainer model until SEO proves itself as a real channel for you. A freelancer spending ten to fifteen hours on content strategy will give you more value than an agency charging £2k a month for a dashboard you'll never open.
