According to the article, around 5% of the properties are being bought by investment companies, leading to concerns that regular homebuyers are being priced out of the market.1) Do you think this could become a long-term issue, given that the current percentage of investor-bought properties is relatively small?

It ranges in percentage but nothing has felt different.

While the guarantee of income sounds great, it's only a percentage of the rent, typically up to 70% and the tenant has to pay the remainder.

Deduct NEW property taxes after you buyDeduct home insurance costsDeduct maintenance percentage, typically 10%Deduct vacancy+tenant nonperformance percentage(we recommend 5% for Class A, 10% Class B, 20% Class C, good luck with Class D)Deduct whatever dollar/percentage of cashflow you wantNow, what you have left over is the amount for debt service.Enter it into a mortgage calculator, with current interest rate for an investment property, to determine your maximum mortgage amount.Divide the mortgage amount by either 75% or 80%, depending on the required down payment percentage - this is your tentative price to offer.If the property needs repairs, you'll want to deduct 110%-120% of the estimated repairs from this amount.Be sure to also research the ARV and make sure it's 10-20% higher than your tentative purchase price.As long as the ARV checks out, this is the purchase price to offer.It is probably significantly below the asking price.

I wondering about cashing in a small percentage of my stock portfolio to fund my next RE deal.  

I'd say my biggest question right now is how to get accurate numbers for when analyzing a deal (specifically insurance and rent) and what's the ideal percentage to use for variable costs?

And like JD pointed out, a tiny percentage of transactions are made using seller financing, and an even smaller percentage of those are done using subject to.

The buyer comp agreement has to be a specific dollar amount or percentage. 

He was happy to allow me to rent out nightly because it actually helps keep his property in better shape than a long term renter (having a cleaner in there every turnover, short stay guests always let you know when something isn't working, etc) but didn't want to hassle with worrying about a percentage of income/management, etc.

With 179 you are going to be limited based on your percentage of business use with the vehicle (so still need to track mileage), and if you go under 50% business use you can end up with a recapture of your prior 179 deduction - income with no related cash flow is always a bit uncomfortable!