Is this a good idea?

I will probably start with micro niches/adsense sites when I am done with my trainee job ( in about 6/8 weeks).

And I've got a liftetime account on dreamtemplates, which has alot of templates for alot of niches. So the only thing I'd have to do is customize them and get some original content for them right?

I'll also save up some cash already to buy hosting for sites.

How much websites should I get ready? Or is this a bad idea?

If you are a new to the whole online thing, start with one, get that one right and then move on to the next. Your lifetime account will always be there