Credit Card Strategy for Sole Trader with Investment Properties?

I was hoping for some advice as I think I can do a lot better with my bank / credit card situation. I am a newish sole trader with credit card expensives around $250k year (most in USA) and have a couple of investment properties which are positive geared. I'm basically just after 2 credit cards with rewards which I can use to better keep track of personal and business expenses. I've never done point chasing before but like the idea but I still need 2 staple credit cards for the above reasons.

Currently I have the following cards:
ANZ - My current bank with just a basic no fuss personal and business debit account as I don't use the cards ever.
Coles Mastercard Rewards - I primarily used this card for international transactions and the the flybuy rewards but since they put point restrictions this is no way worth if anymore for me.
28 Degrees - Have had this for years and have the price guarantee addon so I'll keep this card and always try to max out maximum refund per year.
AMEX - Qantas Ultimate Card - No longer want this card.

Someone once mentioned but did not go into much detail that essentially I could put all my money earned into my investment offset and then I just get a credit card with a long interest free period and as long as this period is longer than 31 days, I can save interest on the loan. What I don't like about this though is that my expenses are high so I would need to apply for a loan with a high limit. Currently my limits by choice is $2k per card but I would imagine I would need to bump this up to $20-$30k in total.

Is that correct and is this still the best option even with the low interest rates we have now? I would also try to find one that gives rewards too.



    OzBargain Guide - might help. Debit & Credit Cards with no international fees

    I think having no Overseas Fee is more important than points, as most cards have some sort of points cap.


    Fake user name? - Saul Goodman would already have a strategy.