Hello,
all the features you've mentioned are not that complex, there's nothing impossible, I've done a similar bot (with paying system via Crypto), with user balance account, buying options, products and so on, so it won't be a big deal.
You also mentioned you need the source code, I can explain you certain things I've done or just comment them, so you can understand what's going on in that class/function/piece of code.
And as I mentioned before, you can test every feature I'll develop and give me feedback, I'll rework on it.
One thing said - it will be an async bot, so there won't be any laggs or delays, because of the efficient async-work.
(sync bots have always delays, specially when there are many users using it)
Best,
Alex