Youth hostels and accommodation in Belgium
Brussels and Wallonia has a number of youth hostels affiliated to Hostelling International
Visit their website at www.lesaubergesdejeunesse.be for detailed listings and online bookings.
If you're planning to stay in Brussels for a longer period, e.g. for a 6 month training or so, here are the details of an organisation that will help you to find a comfy and affordable accommodation, through one of its flat-sharing or studio renting facilities. Its name is brusselsdestination
Remember that whilst you are in Belgium, there are a number of youth rail passes providing unlimited travel for one low price. The interRail Benelux Pass allows for 3, 4, 6 or 8 Flexible days unlimited
Alternatively you can purchase the Benelux Rail Pass which is valid for 5 consecutive days of travel. Further information available from www.InternationalRail.com and www.raileurope.com