I was looking for something that can hold all of my marketing leads, customizable with drop down leads, searchable and maybe even have some sort of mail merge feature.

it's the easiest most customizable thing I've found so far.

It's one of the (if not, the) most popular blogging architecture and it is very customizable with a strong community constantly producing and updating plug-ins, themes, etc. for it.

Most of them will let you set the polling interval, however, not all of them are fully customizable so you can set it to 1 minute or whatever your personal update urgency level is accustomed to ;)Depending how badly you want it, you can jump through hoops and have email forwarded to gmail or somehow have gmail collect from other POP accounts.

WORDPRESS-By far is the most user friendly and customizable tool if your wanting a mobile website.

I would recommend using a service that provides rent receipts, customizable rent due email notifications, automatic late fees, and some kind of tracking or record keeping of these payments.

@Kalen Mills listsource.comVery inexpensive and highly customizable lists.

Everything there is also customizable. 

When I was managing 20+ in Denver Airbnb kept them all booked (Booking.com, VRBO, etc never provided any value, just a time sink to use a clunky channel manager), I use Price Labs for pricing, which is the most customizable price tool if you have a good base knowledge of your market.  

I have 30 doors and need something that's cheap, customizable, and feature rich.