If you start bending your rules now to accommodate, you will be doing that the entire lease.

Our family is growing (I am expecting) and are in need of more rooms to accommodate all.

The agent is only looking for a 9 month lease with a month to month option and is offering to pay a premium (+$400/month) if I accommodate her request.

I've been in probably 1000s of houses in Irving and I think I've seen 2 with ADU type accommodations. 

@Jay HinrichsI did actually consider lowering the price about 4% than market value to accommodate the 5% realtor fees.

The vast majority of my transactional experience is in commercial real estate, and owning property in entities is standard practice in CRE but it should also be noted the properties are encumbered by commercial loans which are designed to accommodate entity ownership.The research I've done by speaking with lenders and reading first hand accounts of using entities in residential real estate tells me there appears to be a barrier if the loans are not portfolio loans and even then I'm told lenders who use an underwriting framework that mimics Freddie/Fannie will not allow ownership in an entity.Someone else posted about using a trust vehicle to limit your liability, and I too think this might partially serve your purpose.

We told her the property and the current tenants in the apartment building (it’s a 5 unit building) can’t accommodate her dog, but she is adamant on moving in per the signed lease (which mentions nothing about her ESA). 

Again, they seemed like nice folks and had good tech and strong market share, but they couldn't accommodate me holding my license in Mass with C21 and in Maine with them - even though their two Mass offices were 60 and 80 miles away from me and despite the fact that I was moving in a matter of weeks.I skipped over C21 because they appear to have almost no market share in the part of Maine where we're moving. 

We are looking for individuals and companies who are looking to partner with us and continue on with us as we work to build new affordable, safe, clean, and comfortable homes to accommodate the gap in available housing for the population.

Give the two weeks and try to be accommodating about scheduling.