Personally I have a few rules when buying used kids clothing.
If its stained, torn or looks like its seen better days (for the most part) it goes. When buying in bulk or lot of times I will attempt to resell anything that I don't like or won't use.
If at all possible I try to pick the times up from the person home. A peek inside the house will tell you wonders about how the clothing was treated. Is there a pet? Do they Smoke? is the place dirty? Aside from pets in the home I have no problem passing on the lot of clothing. Smoke is a hard thing to get out of clothing and if the house is dirty or run down, chances are its crappy clothing in ok to poor condition. I have never regretted walking away from an item even if i went out of my way to get it. For most people simple seeing the address and knowing what that part of town is like would work. However where we are it is hard to tell without seeing the house because we have million dollar homes next door to trailer parks.
My final rule is to (generally speaking) not pay more than a $1 an item regardless if it's name brand or not. This would obviously change depending on my location. In NY where my family lives the average cost of children's clothing is about 25 cents an items so I like to follow the trend for the area i am in. I have however spent more for a single item that was too cute to pass up. That being said thought I also did my research looking at prices so I didn't get robbed. I know you spent $20+ on that name brand outfit but I won't pay $10 an item, regardless of how little use it got. To me if I am going to drop that kind of money it will likely be me investing in a few really nice items that I want to pass on from one kid to the next within my own family not for something you want to get rid of.
Granted in a box with 200+ items I could be selective about what I wanted to keep and what would go into the resale pile. I mean nothing with stains was sticking around and I only kept a handful of onesies and bottoms that looked like that had seen better days. After the first night of spaghetti I can use those outfits and just throw them out without worrying about ruining a good outfit.
I sorted and washed the items the day that I got them home. I have super sensitive skin so normal tide detergent will irritate my skin rather quickly. Then there is also the fact that I am a clean freak and like to make sure that everything is clean going into the baby's room. I will admit that the most annoying part of this process was sorting all the items by size. when you are looking at boxes that cover from newborn to 18 months it quickly becomes a pain in the butt.
This is the second set of clothing I bought.
Then my sister in law sent me all her baby boy clothing that my nephew outgrew already.
Needless to say I have way more than I need after all these clothing came in. That being said I need not for anything newborn or 0-3month items as this is the bulk of what I picked up. Lets just hope this baby isn't huge and passes over those sizes in a day.