Code in all areas insists that plumbing of such a scale needs to be done through a licensed plumber. now you are free to remove and install new toilets, sinks, repair drains, even replace supply lines. With that in mind.... different areas have different building code when it comes to all things plumbing. Some areas have a rule about how long the run is and how many fixtures are attached to that run which determines which size pipe you can use. Others have code which sets the 3/4 (or larger) pipe for all runs, and all branches which are less than X amount of feet long may be 1/2 inch. Some areas do not have any preference. There are more products on the market which are cheaper than copper and easier too install. there is a 'new' plastic pvc pipe which is rated for hot water and interior supply. Its an off white color - some areas allow it. There is also a new 'tube' system - basically the supply comes into the house, is divided through what amounts to a 'switch board' and then an individual line to each fixture is installed. This has its advantages, such as no solder joints, no need for elbows, T's etc and the net result is that when a person flushes the toilet a person is the shower doesn't lose cold water. Flow is the important aspect as to why one would desire to use the 3/4 inch pipe over the 1/2 inch pipe. a single run from where the water enters the hose to the kitchen sink may be ok, since its splits off from the supply, but running to the bathroom and having the sink, toilet and bath/shower on it leads to problems if say someone is showering and someone flushes. Distance is also a factor. If the supply comes in through the front of the house and your bathroom is way at the back you loose pressure with the farther the run - And cavitation plays a roll (due to to small of a diameter water can create bubbles which 'jack hammer' the interior of the pipe, effectively reducing the life span of the pipe which can lead to pin hole leaks in the wall - a very bad thing to happen. 1000 square feet is not enough information on which size pipe you should go with.