Your PC wont matter much for youtube, but your internet upload will. Though a faster PC will mean your videos render faster. Anything modern like a Core i7 will do. Ram is cheap so just max out what the motherboard can take. Think typical is 32GB though 16GB may be better budget wise as once you get into the bigger sticks then there is a decent price difference.
Unless you have like P3 with 128MB of ram I would not worry about upgrading the PC just now. See if you can start to make money first.