I have nothing to PM you that is magically insightful. And, I feel like you asked a legitmate question, but unfortunately couched it kind of as a 'I am n00bie, hold my hand for uber pts plz' post. Ergo the somewhat unjustified flaming.

But as a fellow self-employed small business owner and avid MS'er, I have two pieces of advice:

Do not do not do not mix your "raw" MS into actual business practice and financial flow. Not only will your accountant (not) love you, but the IRS will smirk while you try to explain the river of dollars going hither and thither. If it doesn't match to the penny, then it's always still questionable. Don't invite that kind of pain.

With that said, you should have no compunctions about getting multiple and various business credit cards... and using them for MS (but NOT for primary business). I have a card for primary business and it remains unsullied by MS.

Sure, I could generate a goodly amount of extra MS by, for example, paying myself in GCs, renting my home office via Bluebird, paying premiums, etc by money orders funded by OV. But frankly, its not worth the hassle that might occur to explain things. I write a check or do individual bank transfers. Penny for penny match with my books. Yay. At the end of the year, I hand my account a cover sheet summary and a small pile of paperwork with month-by-month accounting.
I do plenty of MS ($25k-40k/mo, depending on how much time I have to put towards it) without having to create business audit headaches.


And finally, no financial institution is going to tell you where the boundaries lie. e.g. "Spend $51,238 on obvious MS junk and you're ok. One cent over and you're hosed." It just isn't going to happen. I don't believe there is an official threshold-- it varies by person, accounts, relationship, history, etc etc.

Find what you're comfy with, ride it for a while and make sure nothing bad happens... *LEARN the organizational necessities to sustain a large level*.... scale up some.. ride it... scale up some... repeat ad nauseum...

But, remember no amount of cashback/miles rewards are worth risking your family's financial stability, and I guarantee (not really) you will hit a discomfort threshold before you hit a bank's red alert button. And that's your equilibrium point.