Shop LTV (or cLTV which is combined Loan To Value, basically your first mortgage and 2nd mortgage combined loan to value), rates, payment terms, time to close,  and draw period (how long you can go into and out of your heloc). 

Currently, we manage approximately 40 short- and mid-term rentals, in addition to a few long-term properties.

From what I’ve read in The Economist, short-term construction loans or hard money financing could be a great fit to cover the $90K needed.

In 2019, I launched my own revenue management agency to help Airbnb owners boost their income and achieve greater returns on their short-term rental properties.

Ditto, I use PriceLabs for my STRs - here is a nice writeup ...Airbnb Smart Pricing Vs PriceLabs: An In-Depth Comparison For Hosts | Boost Your Short-Term Rentals

Some developers go above and beyond on kitchen appliances and install a package that may make sense in a $1.5M+ house in a $900k house but short change all other areas of the rehab.

If it's on the higher side you may want to consider it for mid-term or long term rental, but if most stays are below 30 it can be viable for short-term! 

I'm looking to build a Casita/poolhouse for use as a short term rental in Summerlin.

I generally look for two things: new homes on the market for sale are they being sold very close to asking price, with short days on markets or not.

I’m also based here and have experience with short-term rentals, property management, and work with investors like yourself.