Making your first deposit means the first date you spend non-refundable money on the trip. Often this is the date you purchased your flight tickets.
Are you thinking of just insurance for your husband? Do you not need medical coverage too?
For costs, it took me 5 minutes to check prices in insuremytrip.com for a 38- day trip starting in May for one traveler age 65. I picked a trip cost of $3500 ( that is again for one person). Prices for regular policies with trip cancellation, baggage loss, medical coverage and evacuation ranged from $156 to $569.
I compared two policies. The $156 policy includes $25k in medical coverage ( secondary), $100k in evacuation, and a 14-day purchase requirement for waiver of pre-existing conditions ( meaning it has to be purchased within 14 days of your first trip payment). A $469 policy includes $100k in medical coverage, $1 million for evacuation, and requires purchase within 30 days to get waiver of pre-existing conditions.
We are younger so our policies cost less ( plus we go for shorter times). I look for something between those two, like $50,000 in medical coverage.