Yes I agree with Rachel. Start with a (good quality) online template first, read it and have a think about how it fits your business, then have a chat to a lawyer about any tailoring you might need.

If you want to do any of your own drafting, I’d recommend limiting this to commercial aspects (e.g. a description of your services, charges, payment terms) – if you think any of the legal content needs tweaking, a good lawyer will have a “bank” of additional/alternative clauses that they can usually drop in more efficiently that a non-legal person is able to, and is also better placed to consider how changes to one part of a document might have flow-on changes to other parts.