If the cost of renting "other gear" is the same as renting tents and sleeping bags for a week, it is worth it to just buy. I was able to pick up a decent tent for not much more than REI charges for a weeks rental. I would suspect panniers and racks and such are the same.

About the only way rentals make any sense is if you are traveling somewhere and don't want to carry the gear with you.

I have a pair of Sunlites that served me well on a couple of trips. Add a small backback strapped to the rear rack and it is plenty space for a 2 week credit card tour. Total cost, around $75 including rack. I have since upgraded to Ortliebs but would still use the Sunlites for short trips.