Property appreciation is compounded monthly (not yearly). This will give you a slightly higher total than yearly compounding. It is advisable to estimate conservatively.
Where else can you get 1). A positive cash flow return on your investment (if rental multi unit property) 2). Lenders willing to finance most of your investment enabling you to leverage your assets and returns. 3). Someone else (tenants) to pay down your debt balance, therefore increasing your net assets (if rental property). 4). Asset appreciation based upon the total value of your asset, not just your out of pocket expense. 5). Liberal tax deduction benefits. 6). The ability and option of taking profits tax free through refinancing equity, exchanges, and other strategies. 7). A place to live that you can call your own (if owner occupied) ?