I am a big fan of sophisticated value adds such as lot splits, coop/tic, leverage laws for multiple unit additions.  

Thanks For Texting check out Launch Control, Lead Sherpa, REI Reply, ROOR or Textedly - Just depends on volume and sophistication you need. 

Note purchasing is a very sophisticated strategy best suited for well funded and highly experienced investors.

It also requires gaining a level of sophistication and knowledge that not everyone has the time, inclination or ability to do.

So it requires more significant or sophisticated value adds.  

The people doing subject-to are quite sophisticated and typically have quite the platform.

We weren't sophisticated enough to call it that, but we were both on board because I liked the potential upside and my wife loved the neighborhood (that we could not have afforded to get into unless we bought a dump of a house).

If you're looking for the all-in-one I'd go with a PM software (others have suggested some) and do what you can with it.Then, as you grow further, look at more sophisticated/expensive options.

When you are getting into raising big dollars from sophisticated investors they are going to want to see a track record and a well thought out and detailed business plan.

from the little I know and its only because i have brokered 50  100 unit apartments the buyers are quite sophisticated and have a lot of cash and have their lenders lined up..