If you could help with content creation (to get engagement of the account) could be considered as perfect way. But you are offering to increase upvotes which is obviously fake and it can be considered spam/scam. If there is real activity then it can be upvoted/downvoted but while you will sell all of your votes will be upvoted.
Its far from obvious and definitely not fake/scam. As long as you post content that is relevant to the subreddits, upvotes will make your posts consistently stay in the front page, massively increasing your traffic.