Almost all of these are bogus, either in whole or in part.
1 - You can apply for as many credit cards as you’d like. You will have to provide an explanation for all recent inquiries (last time I was required to do this I just had to check one box on a form and sign the form). The underwriter may want to verify that you haven’t created any new debt with the new cards. This is more work for the processor, but boohoo, you’re paying a fee to have your mortgage processed.
2 - If your new car payment doesn’t blow up your DTI, get the car if you need one. Make your mortgage company aware of the new payment so they calculate DTI correctly. Also, some people pay cash for cars. Yes, really, not everyone strings out payments on everything they possess.
3 - A job change within the same industry is generally construed as continuous employment. New job may require an offer letter/other additional paperwork, but it won’t disqualify you for the mortgage.
4 - As long as the account has no balance (which it shouldn’t) and you aren’t carrying substantial balances on other cards (which you shouldn’t), close credit cards if you want to. Your average age of accounts will not be impacted because AAoA includes closed accounts.
5 - Buy all the furniture you want. If you must finance it, just make sure the new payment doesn’t blow up your DTI. If you are one sofa payment away from blowing up your DTI, you are in too fragile a position to buy a house.
6 - You can spend all the savings you want if you have sufficient reserves. If you don’t have sufficient reserves you are in too fragile a position to buy a house.
7 - You can move money around all you want. You can take a pile of $100 bills and bury them in the yard, or douse them with lighter fluid and drop a match. The only transfers you have to document are for the accounts that hold the required reserves. You don’t have to declare every account or every shoebox full of money on a mortgage application; in fact, over-disclosing just means you have to produce more paperwork.