Are you planning that the girls visit you or that your boar goes out to them?
If the girls come, then you need secure area away from your sows (to minimise disease spread risk), and work out how they deliver all year round - ie ability to reverse to pen and unload in all weathers. Cost of feeding them whilst they are with you need factoring in. If you sell litters, then unless he and girls are in approved isolation area, you need to phase arrival and departure to prevent standstills on selling your weaners.
If he goes out, then again an isolation area (whether official or not) for when he returns to ensure he brings nothing back in with him, or that you can treat before he infects your girls. Are are you delivering or are they collecting? in both cases, again all year round loading/unloading. If you deliver, then time and diesel needs to be factored in.
You might want to consider possible damage to him, or him damaging sows and them claiming against you.
You'll also need a written hire agreement 1. if you take the girls to prevent girls getting left with you without recompense - not just feed - imagine if someone delivers two girls, then says they can't collect because their ground is not reachable due to rain, and you end up housing them for several months, preventing you using him on yours or others, and bedding, water etc. for girls ! 2. if you lend out boars - they say that the boar can't be collected as they are on standstill - actually they're using him for other girls on the quiet. You can't hire him elsewhere, or miss being able to mate your girls as he's out.
Sorry all the above sounds very negative, but go into it with your eyes open you'll be fine, but expect everyone to play ball with you and you'll soon find that they don't!!