They could ask for an out if they're unhappy with her service, a reduced timeline, an exception if they are working with an agent in a different market or for a different product in the same market (example: one agent for their residence, a different one for an investment property), if they buy directly from their uncle who is a builder, etc.

Is this common or am I stressing out for no reason?

That just reduced the number of financed properties.If you're married, shove each loan into one spouse only.

That will help reduce the overall premium as well. 

., I haven't heard that term either, but a quick Google search reveals it basically means making it permanent so the bank can't close or reduce it on a whim. 

Current financing available, construction costs and how to reduce them, appraisal trends, best practices when building on investment properties, rental values, design trends, how to minimize the construction time, ideal target markets, which city's DOB's are helpful and which aren't, preferred vendors, etc.

If you can't Airbnb it, I would suggest offering them a reduced rate to be able to keep their stuff there for the summer.

If it were me, and I could get some significant cash out or reduced rate, I would do it now.

If you numbers can absorb the extra cost of the full term interest and you value the convenience and slightly lower stress, than it's not necessarily a bad strategy. 

Bernie Sanders wants a 25% “house flipping” tax levied against investors who sell a property at a profit within five years of purchase.He also wants a 2 percent “empty homes tax” on the property value of vacant homes in order to discourage real estate investment.From Bernie's Website"When Bernie is president, he will:Create an office within the Department of Housing and Urban Development to coordinate and work with states and municipalities to strengthen rent control and tenant protections, implement fair and inclusive zoning ordinances, streamline review processes and direct funding where these changes are made.This office will convene key leaders, academics, experts, local officials, renters, tenants, and homeowners to create and implement these necessary solutions.Preempt laws that prevent inclusionary zoning for luxury developments.End exclusionary and restrictive zoning ordinances and replace them with zoning that encourages racial, economic, and disability integration that makes housing more affordable.Require that recipients of federal funding from the Department of Transportation and the Department of Housing and Urban Development make these important zoning reforms.Provide funding to states that preempt local exclusionary zoning ordinances to make housing more equitable, accessible and affordable for all.Make federal funding contingent on creating livable communities.Encourage zoning and development that promotes integration and access to public transportation to reduce commuting time, congestion and long car commutes.Prioritize projects that reduce greenhouse gas emissions, create walkable and livable communities, and reduce urban sprawl.Encourage zoning and development designed to expand and maximize the number of units fully accessible to people with disabilities.Place a 25 percent House Flipping tax on speculators who sell a non-owner-occupied property, if sold for more than it was purchased within 5 years of purchase.Impose a 2 percent Empty Homes tax on the property value of vacant, owned homes to bring more units into the market and curb the use of housing as speculative investment.Encourage “circuit breakers” on property taxes to protect homeowners in gentrifying neighborhoods from being priced out of their own homes as their property values rise.READ MORE: https://berniesanders.com/issues/housing-all/From my point of view, anything that impedes or obstructs REI's cash flow is a bad thing.