I did not have a lot of evidence in our initial application, mostly because my husband and I had just decided in February of 2017 that we were going to move to Canada. I had wanted to move back for a long time, but we only recently started planning it. So at the time of our application, we didn't have a super detailed plan yet. I included a 2-page statement of intent in our original application and some evidence of housing research/planning. I indicated at the end of my statement that I could send more info as we progressed with our plans, because I read online somewhere to submit what you can and if they need more info, they'll ask for it. I was approved as a sponsor in November so I figured what I submitted was sufficient. But sure enough, they requested additional info from me (sponsor) once they started my husband's (the PA) background check. Here's what I included the second time:
-updated statement with the progress of our plans for housing and jobs
-letter of support from my brother in Toronto attesting to my plan to return to Canada
-letter of support from my aunt in PEI " " "
-letter of support from my husband's current employer stating his knowledge of our plans to move and his support to help my husband transfer within the company to a Canadian location
(these letters weren't notarized, but they were all written on each person's respective company letterhead to show credibility, and included their signature and personal contact info)
-copies of emails spanning several months between me and my family (brother and aunts) discussing my moving plans
-screenshots from my computer search history showing apartment & job searches, spanning the past several months
(luckily I don't regularly delete my search history)
-email correspondence with rental properties
-email to a Toronto company inquiring about a job position
-copies of flight itinerary from my two most recent trips to Toronto to show that I've maintained ties to my hometown
(luckily I still had copies of these flights in my email inbox from booking my tickets online in the past)
I know it sounds like a lot of extra info, and I probably went overboard, but I had to include as much as I could because I have been living outside Canada for over 20 years, which can be harder to prove intent to return. I moved away with my family when I was a young teenager, and therefore I didn't have proof of a job that I was returning to, or any property or bank account or anything too official.
If you're looking for ideas of what to send if or when you get a similar request, it's good to document all your moving preparations such as saving copies of emails when you've inquired about apartments or jobs, or emails sent to friends, etc. I basically had most of this already on my computer - the only additional thing I did was to ask for the letters of support, which people were happy to do for us.