If this illegal, probably it could be an upvote buying or vote manipulation which is against their terms of service, and this will breaking their TOS. The result might be taking down your account.
If not, then makes all things be clarified with full details and use escrow service since you're a newbie and don't have the credibility to run a service like this, it might be a risk to those who will join.
Whatever is this, it seems completely illogical. unless the earnings are in the form of dust.
There where are many services where is possible to buy upvote/downvote etc... Also if OP had a serious legit business and they just need Reddit account, why not buy them? As far as I know, Reddit account with solid age and karma can be purchased for just $15-$20. Not a big money if the can help to earn.
btw. trading with the vote, likes, repost... is not allowed on almost all platforms but it is still a serious branch of business.
whats worst is if the deal is illegal and the payments are also dust but if its legal and the payment is dust im not sure if there will be interested participants that will try but this could be their intention to try to save up some cash because they can just do what you have suggested above but still insist to open up an offer like this .
trading votes likes and repost and illegal but why there are still sellers of those service ? and worst is that they are mostly being sold on this forum and mods didnt take action with those service , wtf ?