They have a portal built into their site, not sure what software they use, but it works well. 

Do you take phone calls directly or use a portal?

www.htownrpm.com Work off collected rent (<8%), no monthly fees, full service maintenance dept, on line portal, great ratings 

The online portal wants you to know the estate's name or case number.

For those self managing landlords, what is the advertising portal that gets you the most leads?

I use rentec direct for a tenant portal and have had little issues with the property.

Portal where investors can access information about their investments with you.

When ordering a draw, you simple go to your online portal, click construction tab, then submit a dollar amount for each budget item.

I use Excel with SumIf statements to summarize data by keyword from other pagesApartments.com for a free rent payment portal that go directly into my bank account so I don't have to hassle depositing paper checks. 

Where just the assets of the business and cash flow is being bought but not all of the liabilities.If the sale is a business and the building then you get into a real estate component.You can look at www.bizbuysell.com which is Loopnets business buying and selling portal.