We have a 40# fryer that holds a jug and a half (about 7.5 to 8 gallons), We change the oil once a week, and may go to more frequently now that our volume has gotten much higher. the 35#-40# model is probably a good starting point as it will have a better recovery time than the table top units (ANY recovery time is better than counter top units!).
Cleaning is not a huge hassle . . . two 5-gallon buckets from home improvement store, a garden hose with sprayer attachment, a good fryer boil product, and about 20 to 30 minutes of time.
We can cook about 250# fresh wings, chicken fingers, breaded ravioli, fried brownie & cheesecake bits, and a couple other low volume and low impact goodies in that week. That is pushing the limit pretty far, though. We use simple, inexpensive soybean oil and do not filter. Not much point with the cheap stuff as it only gives you one more day, two at most.
If you are using french fries, the higher quality the product the less stress on the oil. Some products have wayyy more water in them than others, and break down your oil much quicker. The length of time you have it heated also makes a difference,ice crystals on the food product, water dripping from food, plus the types of food you fry.
