In that case, the invitation letter would be from your friend/customer.
You would be applying for a Business TRV for a well-defined, finite visit.
You would need to prove you have a business relationship to your Canadian host + a day-by-day itinerary of what you intend to do + hotel reservations and flight bookings (both provisional, not confirmed) + why you really need to visit versus why the same meetings cannot be done over the phone/emails
Basically, you would need to convince the visa officer that you will not work illegally when you visit + you have strong reasons to return to your home country. IMO, this could be somewhat challenging as you work as a freelancer/can work remotely because you don't have an established workplace.
You would need to work hard to prepare the paperwork: Family ties + property/land ownership + good financials + previous travel history, etc