1. Enjoy exploring and just vist loads of other shops until you see somewhere that has a store or land for rent
2. This is very useful but will probably mean you pay more for the store
3. Yes and No. If its too similar they will maybe just ignore yours as they have the items at the other store
4. Impossible to rely 100% on anyone. This is why buying mainland is a good option.
5. You own it, it wont be taken away from you.
6. Think about expansion... is there room to expand the land are or prim count