For practice wood, look around at local business that have pallets sitting outside. Some have to send the pallets back, but with a little looking you will have as many as you need to work your skill level up.
Other practice wood, look around for some one taking down a house, barn or fence.
For other hard wood, look up saw mills. Have a local I bought wood from that lets me go through his scrap and off cuts for free. That is if you have room to let it dry out before use.