Some Advice Please

I'm new and don't know much about SL. I like what I see and have some ideas I'd like to persue.

1) I'd like to build one of those city buildings (seen in London) where the store is below and the apartment is above it. Usually in movies and such you see a line of them seperated by a doorway stairs leading up to your home.

2) I'm thinking of a petshop. A variety of dogs and cats and fish to start out with. Maybe farrets and parrots later. The shopper can buy and take home...and have to feed it every so often to keep it alive. Pet food will be available at the store. Pets will get roudy if you don't show the attention once in a while.

3) once I get enough money, I'd like to take on some land and build a golf course. People (for a fee) can play 18 holes and try to bertter their last score. Equipment will be available at the stores like clubs, balls and such.

thats all possible.. however first start step by step.. slowly ..
start learning how to build small house... for pet shop nice idea similar to tamagotchi toy in RL.. however you would need to learn some scripting.. or if not.. just hire somebody who knows... good luck

Agreed, although your first two aren't so hard to do once you get a grasp on building.
I'd definitely start with the building first as it'd be simplest, and it's similar to how I built my store. Now mine is a tall tower but the principle is similar (shop on lower 2 floors, house on top 2 floors), I built the basic shape using cubes which I hollowed and then cut to form corners (rather than using separate cubes arranged as corners). This is a good way to reduce the basic structure to only a few prims
Now, one thing I did was to remove my house from the store, okay I built the part where my house would be, but left the inside empty. I then put the house itself in a separate box hundreds of metres above the building, then where I would put a normal door to get into my house, I put a teleporter that takes me up to this sky-box. It's really worth looking into doing that as it keeps shoppers and visitors to your home apart so you can chat with friends in your home without hearing shopper's conversations (and without them hearing yours). I'm sure there are some free teleporter systems around (since they're not hard to make) that you could probably change to look like a door so it looks nice.

As for pets, have fun
The building can be tricky at first but most of them can be simplified into basic parts and the shapes used in SL. The most difficult part is finding ways to reduce the number of primitives you use to build them, though you could mb post pictures and people will suggest ways to reduce the count.

I wouldn't get into scripting right away, but if you're doing this on First Land you may have to to keep prim-counts manageable, for example having pictures of your animals that users can click on to see the real thing.