My BK lawyer said it was ok to open a secured card before the discharge. You should be ok, but I would run it by them first.
I agree with Tooleman. You should be ok. DW and I both got our Discover secured and Cap One Platinum cards a few week before our ch7 discharge. But it's always advised to wait till after your discharge to start applying for new credit.
I receive many calls from folks in active BK Chapter 13's interested in the possibility of purchasing a home. First thing I tell them (if they haven't already done so) is to open up a secured credit card or two. Specifically, one that allows you to increase your credit limit by increasing the savings account balance. Why? Because you'll get a secondary bump in points when they report the increased credit limit when you can afford to do it. That said, I have contacted many Attorneys, and all have said "Secure Cards" while in a Chapter 13 is not an issue.
As it relates to qualifying for a home, you can be approved for a government loan such as an FHA, VA and USDA Rural Development Loan while in an active Chapter 13. All you need is 12 months on time payments and approval from the Trustee. We go down to 580 middle credit score across the board on government loans. I have helped hundreds of individuals and families get into a home when they thought it wasn't even possible. Hope this helps you. Let me know if you have any questions.