I wouldn't waste money on a castrated boar that you feed, year in, year out.
Work out what two sows would cost you to feed in a year, and research your local market re. demand for weaners and meat. See what the demand is and then see if it's feasible.
If you decide to hire in a boar, bank on paying £50 per sow. AI (if you can do it) will be about £24 per sow.
Spend a bit of time working out your business plan - even if it is, essentially, a hobby - before making a big commitment.