Q1. No, absolutely not! The last thing you need when first starting out is overheads. If you don't have the space, buy smaller lots to get you going, or bum some garage space of a friend to store a pallet.
Q2. Pallets will vary in size, but a full pallet will be about 4x4', and then will vary on the hight with each load, but some card-boarded pallets can go up to 6 or 7 feet high.
Q3. That is your decision, if you intent on running it as a business, then a Tax Id will be required, but you won't need on to purchase from a liquidator, they aren't wholesalers.
Q4. Yes.....knowing your shipping costs is a must or you risk ripping yourself off with the shipping.
The non liquidation question, sorry...can't help much with that one