A) That's my primary advice, too ... live off of one paycheck. The only think deducted from my paycheck was (1) the added taxes, (2) daycare, (3) my personal work expenses (gas, clothing, etc).
B) As soon as you become a SAHM, change your hubby's tax withholding to reflect the change in income. Changing his withholding puts more cash in your pocket. Don't use your tax refund as a savings account. You need the money now.
C) As soon as you become a SAHM, keep saving. Have an automatic withdrawl taken from your hubby's paycheck and deposited into a savings account. I know money is tight but it is important to continue the saving habit. Live on LESS than hubby's paycheck.
D) While you are still working, pay down all your debts. Obviously pay off your credit card debt if you can. Stop the habit of using credit cards to make purchases.
E) Recognize that being a SAHM will mean some of your expenses will INCREASE. When you work your car is used to commute to work and back and maybe a little bit of driving during your lunch break. When you're a SAHM your car can be used all day long - AND FREQUENTLY IS! Plus when you're home you will be running the furnace and A/C all day and using other utilities more than you do now. When you're at work, you use their bathroom, for instance. Now you'll be using your own. And the temptation to continue to eat out or get take-out will NOT go away.
F) Recognize that being a SAHM can be very isolating. As above, you will want to shop or eat out MORE, not less, if for no other reason than to be out in society and away from home. Many people (almost all that I know) who suddenly stop working go through a period of depression. When we stop working we have to re-define who we are and our place in society. It isn't easy. Have a support network set-up. If anything become too busy early on - enroll your children in classes and playgroups, etc. Join organizations like MOMs Club or MOPS. You will probably find yourself making new friends since most of your acquaintences are work-related.
G) Be realistic about how much you can get done around the house when you're not working. Daycare is expensive for a reason. Those other people who are taking care of our children really are doing a real job (hopefully). When I worked we had a housekeeper which was wonderful if for no other reason than to validate for me that cleaning my house had a real dollar-value AND did take time. You might be surprised how little you will get done during the day.
H) While saving money, set aside a separate bank account for yourself (not joint with hubby). While my husband is extremely progressive when it comes to my independence, we have had arguments over money when I no longer brought in an income. He had to go through a psychological transition, too. Suddenly my income was no longer a safety net. His role in the family shifted when I stopped work, too. Don't be surprised if your hubby suddenly feels like he has to work MORE (instead of come home to enjoy time with you and the kids). Anyway, one Christmas I was fretting over what to get hubby as a gift and he said, "Don't get me anything. You'd just be using my money anyway." His attitude surprised both of us and we did have a long talk to re-align his thinking BUT it is still nice to have an individual savings account of your own.
I) Increase the life insurance on you or buy a new policy. When we work our employer usually provides some life insurance. You won't have that anymore. As a SAHM a life insurance policy on you is more important. After all, if your hubby dies you could always go back to work. If you die, your husband will be in dire straits to find household help, daycare, etc. Of course, make sure hubby has enough life insurance, too. You don't want to have to go back to work soon after a family tragedy. Similarly your husband should have disability insurance - a private long-term policy - to help with the financial hardship that would come along if he was injured at work. You won't be in the position to work if you're at home taking care of the kids AND your husband. Of course, update your wills and make sure that all bank accounts, house, etc will automatically transition to you in case your husband suddenly passes away.
J) Have an exit plan. Anytime we start a new venture, we are prudent to have an idea of when it isn't working out. So set aside dates now where you will re-evaluate your decision (6 weeks, 3 months, 6 months, etc). See how you're doing financially. How are you doing emotionally? How are the kids responding? How is hubby transitioning? What do you have to do to adjust or improve? A problem doesn't automatically mean you will go back to work fulltime and return your kids to daycare but you may decide to try other solutions. I don't know any SAHM who never did anything except stay-at-home the entire time their children were children. The more you live as a SAHM other options will become available to you. However, don't feel like you need to jump on the first idea that comes down the pike. Try to remember that the more we fill-up our day with one option, the more we block other options from coming into our life. Remain open, listen and observe. The perfect balance of takng care of your marriage, your children, and your personal life will eventually come to you.