There are many options for accommodation.
You can either stay in the Centre of Edinburgh and travel to the training school venue by bus, or stay in Portobello and walk to the training school venue.

The route of the 26 Bus

All prices here are indications, check before you book

There are many other options that can be found online

In Portobello

Straven Guest House ~£45/night
About 15 minutes walk to the venue

Anderson Guest House, Piersfield Terrace
About 20 minutes walk to the venue

Premier Inn Edinburgh East from ~£40/night
About 20 minutes walk to the venue

Seabreeze Bed and Breakfast, Seaview Terrace  ~£50/night
About 25 minutes walk to the venue

Best Western Kings Manor from ~£55/night
About 30 minutes walk to the venue

In Edinburgh centre

Some budget hotels 

Easy hotel, Princes Street from ~£25/night

Travelodge from ~£40/night
Rose Street
Princes Street
Waterloo Place
Queen Street

Holiday Inn Express, Picardy Place from ~£40/night

Mercure Hotel, Princes Street from ~£50/night

Some hostels 

Caledonian Backpackers, Queensferry Street from ~£15/night

Haggis Hostel, Princes Street from ~£20/night

Edinburgh Backpackers, Princes Street from ~£12/night