Sophie,
my (now) husband tried for a visitors visa to Canada last year.
You will need to have your letter of invitation notarized (I believe it cost me $60.00).
My letter stated that I would help pay for his ticket, provide accomodations, travel arrangements and food for the 2 weeks he wanted to travel here.
He took in his application paid the fee and was told to come back in 2 weeks time.
When he went back he was given a form letter with some reasons checked off for the denial.
1) He did not prove that he had enough funds for his trip
2) they did not believe his intended purpose of the trip
3) he did not satisfy the officer that he would leave the country when he stated he would.
When bob mentioned having money in the bank - it's several thousands of dollars and even then it's no guarantee. I won't tell you to not do it - but keep in mind that it will be a very slim chance that he will receive it. I had not searched this site prior to his applying - and we were both very disappointed when it was denied.
Best of luck
