Reggression and tests needed

Let's assume that we have to examine house prices and we have 5 variables.... PRICE,SIZE ,AGE, MANHATTAN(MANHATTAN= if it is located in Manhattan) and TAX. And i have 3 questions : 1. how can we generate a model that calculates the PRICE of a house according to the other variables. 2.HOW can we tell if it is statistically important if house is located in MANHATTAN? 3. WHICH are the tests needed to be done in an example like that to be valid? ( normality?residuals homo etc) Of course i need the answer in R programming