To all Freelance SEO-Consultants: how do you charge money

I am a freelance Web Developer in Europe and consider myself good enough with Google Search Console to optimize and monitor the Search Results of the websites which I develop.

My question is: do you have long term SEO contracts? If so how do you charge money?

My goal is to combine this "SEO-Maintenance" with my Hosting Service to have some additional monthly income.

My customers would be smaller businesses with only a few pages on their website. Honestly there is not so much work to do, I expect like 30min per month.

I can charge around 10-15€ a month for hosting.

I wozld really appreciate your help! Thanks and all the best!