Welcome to the board, congrats on the little one to come. It's great that you're considering cloth, it is indeed less trouble than it used to be and much easier than most people think.
Convenience is all a matter of perspective unfortunetly. What's convenient and works best for me, may not be what you prefer. All diaper types/styles have their own set of advantages and disadvantages. For example, pocket diapers or AIOS (All-In-Ones - they have the diaper and cover all in one piece) are usually seen as the ultimate in convenience because they're just one piece to put on the baby - just like a disposable. But they also tend to be a little more difficult to wash, pockets especially.
For what it's worth, I love fitted diapers. I've had 4 children and have tried dozens of different types of diapers and covers over the years. ME Sandy's with Airflow covers are by far my favorites!
Used diapers are a great way to save a little money. The quality of diaper you get can really vary though. You can find some that are essentially new, having been washed once or twice if that. While others will be more used, having been through a couple of kids already. It really depends what your goal is and just how tight your budget is. Also if you're planning on having more children or not may affect your choice to go used or not (wether you need the diapers to last through a couple more children or just the one...).
One bit of advice though, washing only every 4-5 days is probably not a good idea for several reasons. First is that this would require an enormous amount of diapers, especially for the newborn stage. Figure that a newborn/small infant will go through about 10-12 diapers a day. That would mean you'd need a bare minimum of 50 diapers to go that long. Chances are that your washer won't hold 4-5 days worth of diapers so you'd be looking at doing more than one load. Most washers typically can handle a maximum of about 24 diapers... You'd also probably need more than one pail. Plus there's also the issue that diapers that have been sitting for more than 2-3 days get very difficult to clean (odors and stains tend to set after too long).
Most people do diaper laundry every 1.5-3 days. It's really not that big a chore honestly. Not much more than a typical load of laundry really. The only additional 'step' that's fairly common is a plain water pre-rinse just to get most of the 'yuckies' out before the actual wash. Other than that it's just a matter of putting them in the washer, adding a small amount of detergent and then pressing start. Afterwards if you like you can hang them to dry or just stuff them in the dryer...
As for supplies you don't really 'need' that much... I'd say about 2 dozen diapers (that's an average number, you can get away with less or invest in more, it's all up to you), 4-6 diaper covers per size (keeping in mind that baby may skip some sizes depending on how fast he grows and his build) and a diaper pail (any large plastic container with a lid will do just fine). Good things to add are maybe 2-3 dozen cloth baby wipes (these actually work better than disposable wipes and you just throw them in the pail with the diapers) and maybe a pail liner (this is basically a large water-resistant bag that you can use to line your pail, then take just the bag to the washing machine, dump diapers in and wash right with the diapers - makes pail cleanup much easier). Once your baby is on solid foods or formula you can start considering stuff to make poopy diaper cleanup easier like flushable liners or a diaper sprayer. If you're exclusively breastfeeding the poopy diapers can go straight in the pail and then just run a pre-rinse before washing (breastfed baby poop is water-soluble and barely stinks).
HTH, don't hesitate to ask us all any questions you may have, I know cloth can seem really intimidating at first...