Home Equity Loans Arizona

I recently paid my car off and I have good credit. Not the best score, but good. I have some money saved up and live on good size farm, but I don’t want to sell my land that I lease out. Plus I do have a full time job and get some money monthly for rental property–little income there. My current home is paid off–inherited and I plan to rent it out as well. I want to build a home on my farm. I am just not sure of the how to go about calculating and knowing the interest rate and all that and to know if my down payment would be adequate. Sorry, but I am clueless to this process. I tried doing an online mortage calculator, but then at the end, I had to give information to get different lender’s offers. I really just want to do this myself to get an idea. Do I have to go to my bank first or is there a way to do this without contacting them first and not giving personal information to other lenders online? I think I would want a fixed rate, but I don’t know the interest rates.