All are great platforms and have their unique features that make them great choices for Real Estate Agents experienced and new.As @Chris Bounds mentioned, it depends on your business.

Great choices here. 

@Eamonn McElroyIf he has a truly self-directed Solo 401k plan then the bank or the brokerage does not dictate investment choices, this plan allows you to invest into virtually anything and which is permitted in the plan documents.

It's nice to know someone will always be on the other line.In any case, making the leap to management software is a great choice.

Be sure your Landlord Insurance is sufficient.

., but you have to bring SOMETHING to the table. ...regardless of what type of value you bring, it has to be sufficiently valuable for the mentor to benefit (and if the mentor is a highly experienced and successful RE investor, their time is extremely valuable, so they ain't gonna come cheap!). 

I see that HELOC is the best choice.

It seems the seller concession is a more favorable choice since that closing cost reduction is provided all at once versus lower monthly payment by say $50-100 over a long period of time, say $10,000 concession in exchange for $50/month payment reduction, that's 200 months (almost 17 years) to break even.

This can be very expensive and is usually the worst choice to make because you can't justify the cost.2.

Zillow is usually sufficient but I like having a few options.