Any help will be appreciated..  I am going to build a good/great preban Carbine with collapsable stock..  Wife bought one today..  Gotta keep up, but step at a time..  Where should I start and how much should I expect to spend???

for just the lower? if your lucky, 650. their are some legallity questions about buying a preban receiver, but if it has a car stock on it, or its never been documented as stripped (IE, private, never been though a dealer since it was stripped) i would only but a complete preban lower with a car stock, unless it was from a friend. now, for 650 you can get a stripped, but fot like 750-850 sometimes you can find a PWA preban rifle. that might be a better starting point.

where can you find those lowers  with a telescoping stock under 900-1000$ its really hard? and what brand are they usually? my birthday is coming up

What part of the country are you in? If your near Phoenix try the Crossroads gun show.

Colt $900 to $1,400.  Lower end for 7.62 or blemishes, upper-end for full A2 without block

I guess my wife did OK with her eagle arms car, "nib" for 1395..  huh?  Got it at Crossroads in Phx Sunday..