When start thinking about mutli DB?

Hi there,
I'm having fun working with WordPress and slowly business is growing.
Now approx. 50 sites in a multisite install and a few stand alone's.
I'm thinking about a private server.

Is that, in your opinion, a step I should take before going to use multi DB's?
Is it really true that you can put several hundreds of sites in one database?

Thx for responding and have a nice day!!