Assuming cash flow is sufficient for your goals, you have high confidence in your income and vacancy projections, and a high confidence in the HOA not changing the existing restrictions, I don't see anything else that should give you second thought, based on what you've shared here. 

Right now, more than any time in recent history, focusing on location and quality over quantity is where you can absorb costs better and generate better margins.

I give tenants 90 days advance notice and ask them to respond within 30 days so they have sufficient time to think about it. i.e. if they want to continue then sign the lease or if they want to leave then give a 60 day vacate notice.

Be careful not to get over-extended as it’s unwise to buy property without sufficient capital reserves to CYA if something expensive comes up. 4.

They can handle any quantity or style, and their sliding and bi-fold doors are also excellent.

When I take on someone to train them, They are usually self sufficient within a year of "one one one" training.

Are there scenarios where the letters alone generate sufficient ROI?

Most institutions won't pay more than 1.5% (and some 1%).  3+% is a solid indicator that sponsor is more focused on quantity over quality.

If your return for investing in another property is greater than 8.5%, than it would be beneficial to invest rather than pay off the debt (would want a sufficient cushion above 8.5% to justify the added risk and work of investing in another property vs simply paying off debt). 

A 'bird dog' is a 'finder'... and while there are clear cases of advertisers overstepping their bounds into brokerage (http://caselaw.findlaw.com/il-court-of-appeals/1546961.html) there are also (many not so clear) cases where a 'finder' is not a broker (http://law.justia.com/cases/new-york/other-courts/2010/2010-20104.html).I would encourage anyone to browse the last link for 'finder' and also to look at the section 'Quality and Quantity of Services', 'Fiduciary Duty', 'Differences in Entitlement to Fee'.