As far as your 17month old goes, I would recommend buying one or two diapers or pre-folds and covers, and see what style or brand you prefer before making a large investment on any one kind. You can tell your husband that cloth diapers can be re-sold used when your done with them, and as long as they're in good condition you can re-coup around 80% of what you spent on them. It really is amazing.
Pre-folds are nice because they are the most affordable. The cover usually stays clean and you can just replace the wet pre-fold with a dry one. The pre-fold would need to be changed more frequently than a pocket diaper or all-in-one because they just don't hold as much liquid as microfiber. If you were to only use that method I'd say you'd need about 2 dozen pre-folds & 6-8 covers, laundry would need to be done every other day. I use pre-folds at home during the day and pocket or all-in-one's when we're out or for overnight.