Draw out your fungible expenses per month (not tithing, car or house / rent)-

Food
Going out
Entertainment
Insurance
General
Phone
Savings
Etc

Evaluate those as best you can to ensure you’re not indulging or going over the top at all on any of them. For example cell phones should be about $100mo for both of you. (As EQ pres it blew my mind how much $ people waste on phones)

Then take what’s left… that is how you know how much you can afford on cars and rent (mortgage)

If you can’t make that work start again.