His mailing list subscription alone will give enough tips to keep your SEO'ing efforts going for a long time.Anyway, in my industry this is the gold standard, the dude is in line with all major search engine algorithm changes and tells you how to adjust your SEO efforts accordingly.

Some costs such as commissions and management fees you can charge them at fair market prices, so after the property is sold, distribute the cash in the following orders:1)  Return the initial investment capital back to investors, you 10%,  partner 90%2)  You take 3% buy price + 3% sale price as commission , plus 10% of rent as management fee 3)  Now see how to split the profit:  think about how much of your time and effort worth (A), and the potential profit (P), A/P will be the minimum share you will get.If there's any loss, you can take 10%, partner take 90%.After you work together long enough, have mutual trust, and know the potential profits well, you may find a simple split like 30/70% .       

Most agents only working part-time dont end up making as much as they would think due to broker splits, team splits, taxes etc and the amount of effort to become good at the paperwork, negotiations and marketing for clients is more difficult than most people tend to think as well.

If I were you I would start talking about succession planning for his rental empire and tell him you have a genuine interest in taking it over or a portion of it.With an estate as big as his tax implications can become a real problem if measures are not taken prior to his passing.

The effort put in to getting the house sold by the agent as well as the title company will net them $$$.  

If it's an area I know nothing about, it will take me a longer and more effort to determine if the numbers do make sense. 

Ideally you'd put some effort into understanding the scope of possibilities ahead of posting a wide open question here.

Just be consistent in your efforts and things will snowball into success. 

If you are willing to put the time and effort they are good investments, but if you dont have your team, or some set of rules to go with, they are no way these houses are free money you collect each month.

Note when a city does a redevelopment effort it is great for the city.