My views on what it costs to maintain a pacer are varied depending on which trainer it is with, their training style and whether they are honest. The return, equally, depends on these variables and the underlying ability of the horse.
As for minimal costs, these would have to be the horses on deals. Less risk, less upside but fortunately you get the same enjoyment when they run a cracking race!
Deals I have been involved with ranged from 30% (owner) and 70% (trainer) for tried horses to 50/50 (for younger horses or horses with more upside potential to the trainer). The risk with these deals is that some trainers just 'sack' a horse without giving sufficient warning enabling you to find a new trainer without having to go begging.
As for paying up, I think the $40-$50 per day seems to be an average. Some trainers charge more but absorb all other costs (shoeing etc.).
Of course, this is just the training costs... then there is the transport, registration etc. [And, of course, the biggest cost in my experience has been dealing with untrustworthy trainers - I will not slander, but suffice to say, I happily now pay premium rates for trainers whom I trust].