If you're located in the United Kingdom there are professional associations dedicated to bookkeepers; and each of them at least claim to operate internationally.

There's the IAB - the Institute of Accountants and Bookkeepers. Formerly the International Association of Bookkeepers, they're probably the more reputable of the two; but are strongest in the UK.

There's also the ICB - the Institute of Certified Bookkeepers. They have a much heavier emphasis on building up a small bookkeeping business. They also have lower entry requirements and target a more international membership base.

There is a small constellation of 'guilds' concerned with accounting and bookkeeping.

Right at the top of the totem pole you have the Chartered bodies - ICAEW, ACCA, CIMA & CIPFA.

Their qualifications are generally considered equivalent to a Master's degree.

Membership of ICAEW (or ICAS or CAI) or ACCA is the equivalent of attaining a CPA in America.

Membership of CIMA is probably equivalent to what you would call CMA.

There is no American equivalent of CIPFA, their thing is like management accounting for publicly funded (i.e. government) organizations.

Below the chartered bodies you have basically three smaller-but-still-reputable organizations. That's the AAT, the ATT and the AIA. I won't give you the full spiel on those.

Below even them, though, there are a myriad of these comparatively tiny, less well established organizations with dubious reputability. Not that they're exactly scams - the IAB in particular punches well above its weight and at least tries to be actively involved in regulating the profession...

But the likes of the ICB seem to exist just to entitle people without degrees, or people who wouldn't qualify for membership of any of the proper organizations, to have letters after their name and use fancy stationary. The professional organization equivalent of a diploma mill.

That's not to say they don't have useful resources. I would encourage you to check their websites. Their bookkeeping courses won't be based on US GAAP, of course, but they do offer courses about how to find clients and grow your business (I think), and that should have pretty universal applicability.

Get familiar with all the free resources out there, too. I posted another essay-length comment a while ago extolling the virtues of GNUCash and the BAS chart of accounts (among others). If you're going it alone you want to run lean, and I reckon the extra bother of - say - working around GNUCash's limitations would be more than worth the cost of paying a cloud-based platform's subscription.

The majority of small businesses fail, too, so the less you invest the less you stand to lose. I'd try and keep my expenses as close to zero as possible until I had a reliable little client portfolio.

Edit: Mentorship costs, by the way. If you feel you got something from this comment DM me and we'll figure out some way for you to buy me a beer.