Please Help get started

Hello All!!

I wand to start with this, but reading, just get me confused. I can not get what do i need to make outbound calls to PSTN not paying for SIP, how can i have may own PSTN gateway, and what connection to PSTN network I need and what connection to the internet for the serwer to have let’s say 300 concurent calls capacity.
I’ve read alot but all i understand thet T1 connection will give me connection to PSTN, but at T1 rates it’s cheaper to use som SIP provider, i’m getting confused here, and i dont understand how then SIP providers can offer the servis at the rates thet lover then cost to them.

Please helpme here.

Thenk you ALL for the help.