How much to charge for SEO work?

So, I have proven strategies for Local SEO, and I've been working on ranking my site. SEO takes a long time to get great results though, so I haven't ranked super high yet. How much should I charge a client per month? I was told $500 CAN. This is for: \- Content creation (blog posts) \- Link building (guest posts) \- Citations (a one-time fee in addition) \- GMB management And how do I keep my client dedicated without a contract? I was thinking of showing rank changes, but ranking can be unpredictable. Would I just show them all of the continual work I did?