Quantitative or qualitative independant variable question

I'm performing a linear regression analysis of the form y = mx + c where y is the amount of water a house uses and x is the number of occupants (in the range of 1 to 6).

My question is: is the occupancy rate counted as quantitative or qualitative? Clearly I can't have 2.5 people but as each value relates numerically to others maybe this means it is quantitative and not categorical?

Can I do a 'normal' regression analysis with my data, e.g. using Excel to create a trendline and associated formula. Would the corresponding R^2 value mean anything? Would it actually explain the % variation in my model?

Thanks in advance

-Rob