You can do a ‘cash out’ refinance on the rental home as a permanent fixed 20-25-30 year loan to pay off the Heloc on the primary and most likely the equity line on the primary permits a ‘re-draw’ to utilize again. 

However the lenders will want to see the permitting completed before they fund their loan.

I'm assuming the developer has already paid for all of the soft costs (architecture, permitting) before you, the investor comes along. 

Avoid paying large sums upfront.Online Payment: Use secure online payment systems to manage transactions and keep records.Permits: Ensure all necessary permits are obtained and required inspections are passed before proceeding with payments.

Ft)The first thing I look at before viewing a property is the permit history.

The number of bedrooms for STR has to match the number of bedrooms cited in the septic permit, so you are seeing homes with 7 BR now have a 10 person STR occupancy limit and some homes that had bedrooms added without permits now being restricted. 

As for the persons you said you would send an application, you may have to just be honest and let them know that since they have pets, you are not going to send an application because you have decided not to permit pets.

@Ashni Modi here's just a few of the major investments happening in Detroit$2.5B New Center by Henry Ford Health, Pistons owner and Michigan State Universityhttps://www.clickondetroit.com/news/local/2023/02/08/incredible-investment-in-our-city-25b-detroit-neighborhood-redevelopment-to-begin-in-2024/$1.5B Investment, 12,000 temp jobs, 6,000 New Jobs: District Detroit Developmenthttps://www.detroitnews.com/story/business/2022/11/15/district-detroit-1-5b-development-to-include-housing-retail-hotels/69649853007/$1.4B Total as Hotel Added to Hudson Sitehttps://www.detroitnews.com/story/business/2023/11/02/hudsons-site-hotel-plans-move-ahead-as-city-issues-permit/71426631007/$439M Gilbert Foundation investment in Detroithttps://www.henryfordmsu.org/news/september-2023/gilbert-family-foundation-announces-nick-gilbert-neurofibromatosis-research-institute

Sounds like a consult with a real estate attorney or perhaps start with a call to city permits/zoning. 

Hardwired and interconnected vs. solely battery operated depends on what municipality or police jurisdiction the property is in, the date of the requirements, the grandfathering rules, and the last time a permit was pulled, which would have probably eliminated grandfathering.