It would be odd/silly for this contingency to run all the way up until the closing date, but I don’t know how you guys do things there.At the least, I’d communicate with the sellers letting them know the sale of your house has fallen through and it seems highly unlikely you’d procure another buyer and close by your contract date....doing a mutual release now would be beneficial to the seller so they can get their house back on the market.

I do feel like a mutual respect is earned in that way.Good discussion!  

Greg:    First, do not get discouraged by anyone, someone else is doing it so you can, not going to be easy.If not done already I suggest to look into this:Enforce that PM uses a great website for rental screening, ones with a background check and choose the best tenants possible.Review you leases to close any pitfalls and enforce the lease to the T.Keep the units in good shape and keep extra cash reserves ( fixing + trip expenses )Tiger than normal lookup on the PM ( have second PM line up ), vacancies, unit showing costs, repairs, fees, etc,  require a once a week normal operations report and a once a month full operations report.Family, friend on virtual assistant that regularly drive by the property and reports to you, or if cash flow allows and deem beneficial you can install security cameras and remote view activity on the property, nowadays there are lots of options.Check if feasible to get a home warranty plan for the units so some pain issues are self-managed by the tenant via a phone call to the warranting companyIn which city/state is the property? 

Numerous times throughout the past few years, I've strongly considered taking the 90-hour course/exam to earn my license here in Indiana, but have heard mixed opinions from local agents on whether or not it would be feasible, beneficial, profitable, etc.I currently have a W2 job as Controller of a midsize beer wholesaler that I do not plan to leave any time soon.

Mutual funds would be better than individual stocks.

I agree with @Irfan Raza about having lower down payments being more beneficial. 

I think I'm getting a ton of value out of the OTAs, especially AirBNB.That said, I do want to move into my own site, mostly so repeat guests can book directly through me - I think there's a definite value to THEM in avoiding the OTAs, and as @Myka Artis pointed out, there's a price point that's beneficial to the renter and the owner once you cut out the OTA fees (that are mostly guest-oriented).  

Then you escape the tax and can invest the money in mutual funds as you want to.

Often this can be done easily by either a) an addendum to the current lease or b) mutually deciding to terminate the lease and enter into a new lease.Typically rent on a unit will be based on the square footage of the unit and a maximum number of occupants.

LLC electing S-Corp status is usually beneficial when flipping houses, but be careful that your CPA helps you with the "reasonable compensation" aspect- as that would be the main audit risk.