I have some cash in savings that I'll need to draw down over the next few years, monthly. It seems like a CD ladder would be the best way to get a better return, but maintain safety and some liquidity. But I don't know how to put into each rung. Say like I have $10,000 and need $100/m. How do I figure out how to divide it up?
Here's an example for deploying $13,000 into a monthly ladder going out 6 months with $2k coming due every month (adjust your numbers to fit this scheme).
$1k of the $13k will be set aside to cover monthly withdrawals as well as some buffer.
Day 1: Put $2k each in a 3 month and a 6 month CD. In shorthand, you have a 3 and a 6.
Day 31: Put $2k each in new 3 and 6 month CDs. In shorthand, you have a 2, 3, 5 and a 6.
Day 61: Put $2k each in new 3 and 6 month CDs. In shorthand, you have a 1, 2, 3, 4, 5 and a 6 and you will have $2k coming due every month at which time you'll get a new 6 month CD. When there are no more 3 month CDs remaining, you'll just roll each maturing 6 month CD into a new 6 month CD (a phone call if not done automatically by the bank).
There are several problems with this.
You have only deployed $4k in month one so you're going to need a high yield MM account for the balance.
It's a lot of time at the bank or online (paperwork) to get this set up
There are 1/2 a dozen or so high yield MM accounts that pay 2.40% to 2.50% and that beats current 3 month CD rates and isn't much less than 6 month CD rates. I'd skip all the hassle and just put the money in the 2.50% MM account.
You might want to consider Treasury Direct instead. This allows you to buy treasury on the increment of $25 face value. You can build a monthly or even weekly ladder using 1~3 month bills.
Even easier alternative is just using money market fund/ETF, or an online saving that pays at least 2.25% APY.
Many banks require a few thousands minimum for CD, which will make things harder.
What you are asking for ($100/month interest on a $10,000 investment) is mathematically possible but impossible now in the real world.
$100/month is $1,200/year, and $1,200 is 12% of $10,000. No banks offer anything near that high of an interest rate. You'd need $60,000 at a currently reasonable 2% APY to earn $100/month.
Every month for 12 months open a 1 year $5,000 CD and in the 13th month you'll start getting $100/month.