What do I do differently to "earn my fee"? 

They give the same $12k in closing costs to new buyer, $24k in realtor commissions, tack on say $4k in late fees, foreclosure costs, etc etc etc  so they “net” $360k.

If that investor hadn't planned it carefully and re-invested that money into the property or even the purchase of another then a recapture fee would hit them hard. 

I mainly want to ask if these assumptions are reasonable and if there's anything I haven't considered:(1) multifamily units in NJ close to New York City, ~$1,000,000, 20% down payment, (2) Using the following assumptions: 4% appreciation rate, 6.5% interest rate and 5.0% refinance after 5 years, $10,000 yearly maintenance fee(3) ~$6,000 monthly rental and assume 3% increase yearly with 5% vacancy rate(4) Based on the above, the calculated IRR if selling at the 10th year is ~19% (considering tax benefits) and ~17% (without tax benefits).

There is a not so inexpensive fee - anywhere from 5k to 100k depending on the program and they take a % of each deal. 

You want to make sure they are properly installed and you don't want tenants moving large appliances in and out of the house as it will cause damage. 

Things they did bad which I wish I had asked more information about:Never involved in the screening of tenantsThey recommended keys for cash by waiving the rent amount buy only collecting fees which they would get not meThe cost to evict is 750-950 yet other companies told me they will include eviction in the priceThe tenant didnt pay in full last month and I was the one calling out to them and asking questions then a few days later I get an email saying something happened with the tenant and they are investigating.You get passed from person to person every week or so.No one told me when the construction was complete and so the house was ready for a week and the post to zillow and other sites was not done.It took them another week to take pictures and then another week to upload it.I was paying 200 dollar a month electric bills while the house was vacant because they left the AC running in the empty property.

Can easily get a 20% referral fee just for sourcing and handing off that lead.

Is $107k your true net, or do you have any other expenses (mortgage, taxes, lodging taxes and fees, insurance, utilities, landscaping, WiFi, etc.)?

You account for the mortgage and HOA fee.