There is a post in the tiling tools section of the forum. Click the column to sort by most viewed it's easily found. I reckon about a grand really.
Good manual cutter around 600mm capacity(sigma would be my recommendation)
Angles grinder with selection of quality blades
Mixer for adhesive grouts slc etc
Multi tool - invaluable for undercutting doorframes etc
Selection of trowels and floats, framing square, chalk line, other such hand tools.
A good set of levels.
Washboy.
There's loads of things you will eventually need but the above is worth prioritising.
Don't go too mental buying all the best brands straight away, but most of the above is worth getting quality because you use them on every job and it enables you to get a quality finish. With any new business, you have to watch the costs closely.