Typical open lines of credit for first time homebuyers would be ...a student loan, an active credit card, a car loan. The days of using alternative sources to establish credit are gone, in the past cell phone bill payment & utility bill payment proof would help to establish credibility for buyers, but now you need to show you can borrow or have the ability to borrow (credit cards) money and pay it back in a responsible , consistent , timely manner.
I would recommend opening a few different types of credit cards to establish open lines of credit , that way you don't create huge piles of debt on 1 card but can show you can manage multiple lines of credit, with a safety net for unforseen expenses to be placed on other credit accounts if needed, ultimately it helps to use or charge and pay off your credit card to build credit or use that same concept in the form of a loan for collateral like a car , a less costly idea would be to buy a different asset, that you do need, using credit,... like an ipad, computer or TV on in store charge acct. , just an example.
The shift in financing for home loans takes into consideration Debt to Income ratio's & credit scores, you may qualify for an in house arm adjustable rate mortgage which is amortized over 30 years.... fixed for 3 , 5 or 7 years... at a really low interest rate 3.5% or better in some cases, you would still be faced with PMI private mortage insurance until you establish 20% equity in the home. The average home owner in WI stays in their first home between 3 to 5 years so a 7 yr arm is a great way to go if you dont have established credit but do have a good debt to income ratio. Typically arms do require atleast a 5% downpayment. The knock on arms is that they balloon or their interest rate may increase in yr 8,9,10 etc if you havent refinanced by then into a conventional fixed rate mortgage.
The rule of thumb is that your house payment with taxes and insurance shouldnt exceed 30% of your gross income, that will help you to manage the new payment without stress. Best of luck!