Several things stand out to me:
...snip...
Car and homeowners insurance are missing in your budget, or is that rolled into something else?
Also I don't see car repairs in there. It looks like you're thinking of one new car every 10 years? You'll need to account for maintenance. Also is that realistic for a growing family?
House maintenance I think is low if you're trying to include depreciation in that -- eventually you'll need a new furnace, maybe new windows, new roof, appliances, and probably at some point want to update furniture, carpet, etc. $1500 a year won't cover all that, I think.
So, I think your fixed budget will be higher than you think, and above a safe withdrawal rate (especially considering you need it to last 50-60 years!). You have to be careful not to be too rosy-eyed and assume too much in the excitement of possibly making it work, only to run into problems and need to return back to the workforce a lot older, out of skills and with a long gap in your resume. I'd be really cautious with your numbers!
I should have included my full budget based on our historical spending from the last few years.
Here is the summary of our expenses that I have wrapped into "baseline" expenses of $23,000 in my first post (I rounded up from $21,698):
Expense | Amount
1. House-Mortgage | $-
2. House - repairs/maintenance (incl. appliances/repairs) | $635
3. House - insurance/taxes | $1,933
4. Utilities-Gas/Electric | $1,757
5. Utilities-Water/Sewer/Trash | $862
6. Utilities-Cable TV | $-
7. Home Furnishings/ Furniture | $243
8. Communications - Phone/Cell Phone/Internet | $724
9. Auto-maintenance/insurance/taxes/license/regis. | $1,466
10. Auto-gas/tolls | $2,128
11. Medical/Dental | $1,493
12. Clothing | $651
13. Groceries/Household (Walmart, Target, Grocery Store) | $5,851
14. Student Loan Payments | $-
15. Education/Training/Prof Fees | $-
16. Childcare/Afterschool care | $-
17. Dining out | $1,042
18. Entertainment/Toys/Fun (incl. ABC store) | $773
19. Vacations | $-
20. Electronics | $769
21. Gifts | $1,243
22. Charity | $-
23. Misc. | $118
24. Cash | $10
TOTAL: | $21,698
I have a separate spreadsheet that calculates and annualizes the replacement cost of HVAC, paint inside and out, roofing, hot water heater, flooring (carpet/hardwood/tile), etc based on average service lives and average cost per item. It works out to around $1500. I added this in on top of the $635 per year we have been spending on other house repair/maintenance/yard expenses. I may need to set aside an extra $10k or so as a lump sum at ER since the HVAC, roof, and hot water heater will be approaching the end of their average service lives (but show no signs of imminent failure right now).
Our furniture/household furnishings expenses was $243 per year historically. Most furniture that we have has been hand me downs or freebies in great condition, or we built or modified ourselves. That $243 may be a little low, however our current problem is a surplus of furniture, not a deficit.
As for cars, I figure something along the lines of buying a $12000 car that is 5-6 years old, then driving it for 10 years and selling it for maybe a few thousand. So around $1000 per year to repeat this over time (x2 cars). With 5 of us, we might need to upgrade in size from our honda sedans we have now although they work just fine for our purposes. And we could probably get by with 1 car if we weren't both working. We live in the city, so many errands can be completed on foot, or on bike. And our bus system is decent and cheap ($1/trip) though DW won't ride it most likely. Very convenient 10 minute ride to downtown (where I work now and used to ride the bus when it was free for me). When the kids are on our dime and driving, costs will spike, so I threw an extra $2000 per year (forever) into our spending plan to account for at least a few years of very high insurance rates and having a car available for them to use.