Rewards card of your choice. Chase Ink business cards have pretty good signup bonuses right now iirc. 

Hard to know beforehand, but whatever cashback card makes it easiest to download transactions into your software. Some banks won't let you after 90 days, only making PDFs of your statements available. I sometimes go longer between downloads since most of my expenses are automated and I don't need to look at Quicken often. It's nightmarish having to type in a hundred transactions at tax time.

Chase Ink was pretty easy to get and has worked fine. 

There are also no doc credit lines springing up that are actually better deals. 

I'm about to get a line with a local provider. 8% interest vs 23% or however high credit cards have been. 

I've got almost $4k in travel dollars from my Chase Ink and Saphire Rewards cards. Another I have is the Capital One Spark Business but that reports to your personal credit report which I didn't know at the time. If you go on Reddit there is an entire forum devoted to credit card rewards with good info, Churning is the name of the subreddit. The Points guy or Doctor of Credit are other resources.

I find this website useful in determining which card to use. Especially if you are looking to travel hack. You can filter by business and preferred vendors.

http://madfientist.cardratings.com/

i like citi double cash, fairly new card...unlimited 2% back, no tiers, no caps and no categories to remember

Since you're from Dallas, get the Citi-Aadvantage American Airlines cards.  We got 60,000 miles for each card for spending a few grand a month, and we pay our insurance on all our units with it and any other expenses that occur.   That's good for 10-15,000 more miles a year.

Citi Double cash is great! 

It depends on what you want to do, we have around a dozen cards.  For generic spending, I find myself reaching for the AMEX Blue for Business Plus the most and my Chase Freedom Plus if I can't use the Amex.  Those are backed with a Platinum business and an Ink for Bold Business that allow me to accumulate those as points and not cash back.  There is a bonus spend combination on some Chase cards and Home Depot also.  Many great blogs on credit card hacking,  just as addicting as BP.  We're leaving next week for a week long Costa Rica trip with no money into the flight and a nice resort stay.

I was watching a webcasts and the presenter mentioned loaning money to landlords "stretched" for the purpose to make a "big" repair and charge 20%. Do you think this could be a "business", seeking out landlords that need cash quick?