For perspective, here we can get bales rolled up for $15-17/bale.  When trading balers is seems like it always runs around $4-5/bale in depreciation.  Net wrap is going to run another $2-3/bale.  Tractor will east up another $1-2/bale and fuel another $0.75-1.00/bale which amounts to $9-10/bale, and budget $4/bale for repairs and on 100 bales you are looking at $1300-1400 cost to bale and could hire it done for $1500-1700; this leaves you $2-300 in profit and assumes you don't break a thing.

Another thing is in season net pricing could run you $3-400/roll.  Break downs with hay down and rain on the way are no fun and you end up paying dearly for from the dealer.  Condition on a used baler is everything, but not all breakdowns are avoidable.  Blow a belt and its $450, cut a tire in ditches and there goes $200.

Unless you intend to do this long term, spending $15,000 on a baler for 100 bales/3 hours of work per year seems like a lot of investment for a small return.