As the other guy said it is not a rule but a guideline. If you are spending more than 30% of your total income in housing costs your expenses are out of balance and other things suffer such as your savings.

Heck some people then look at it as if it was a goal, which is also off the mark. I make good money, I could afford a lot more house but it is awesome that my current mortgage payment is only 12% of my gross, it makes it super easy to find money to save.

Most of the time what you need is not a budget app but and expense tracking app. One that allows you to use categories but that don't care to track account in and outs. At the end of the month you just look at your budget spreadsheet and input the totals.

I use smart receipts plus. When I buy something be it in cash, credit, Amazon, or what have you, I track it. Just the act of tracking saves you a ton of money because it makes you very conscious of money flowing out on stupid things that don't even make you happy.

There is a free version of the app but if you want to upgrade to the full version from it the option is a subscription, or you can delete it and install the full version for a flat cost.

Just Google HYSA rates. I would also check nerdwallet, I trust them with their assessments.

Why have them locked in a CD for any length of time when you can use an HYSA that has both full liquidity and a higher rate?