In our area of Central Portugal, we find €10-15 seems to be a good working assumption; the higher end tending to involve more experience/skills or equipment.
There are people who will work for under €10; and those aiming somewhat/considerably higher. These rates don't account for materials/consumables.
Naturally, you'd expect to pay IVA @ 23% if getting the work receipted. If you're using a business rather than a person, you'll pay rather more (+/- double) as the rate will cover their operating and employment costs.
I think you're looking in the Algarve - I suspect this gives you more options, but perhaps higher prices - but others can advise on that.