I will start to put new base trim up in a few weeks from a foreclosure I had purchased. My question is the old carpet is out and I need to know how far I need to come up with trim so new carpet will go under neath trim. I will be putting 1/2 padding down and plush carpet. And I also need to know what I should do about the downstairs. The first floor will be 3/4 hardwood floor except for 2 rooms. How can I make base board the same level if plush carpet is only about 1/4 thick and hardwood is 3/4.

You can install your baseboard an 1/8" above the existing wood floor. The carpet installer will butt the carpet to the base , not go under it. If you want a cleaner look install quarter round after the carpet is in.

What is separating the 2 rooms from the area with hard wood flooring? If a door or trimmed arch then height will not be noticed.

U will need a reducer strip from wood floor to carpet.

The other way, but more expensive, is to put 1/2'' plywood floor in before carpet.

Chuck