As PP have said - a limited company comes with costs.
I run two myself. The only statutory costs are £13 per year for a return to Companies House.
I also have software to prepare the accounts on - but then, I am an accountant.
If you are not, you are likely to need one to do this for you. Accountants, even small ones, are not charities. So, all things being equal, they would tend to charge around £1000 to do all the work required for a limited company.
This is why, generally, limited companies are not recommended until annual profits are over £20k.
Given that MLM schemes generally struggle to break even for the majority of cases, there really is no point adding to the complexity by trying to run it through a company in my view.
So, I would suggest you start out as a sole trader. This requires registration with HMRC which you can do from their website. The only requirement is that you file accounts each year by 31st January following the previous April.
You do not need a business bank account - but most accountants would advise one in order to keep your business and 'home' life separate.