This can help offset your mortgage and other expenses.Single-Family Home: If you choose a single-family home, you may have the option to rent out rooms or a separate unit if there's space, but the income potential might be lower compared to a duplex.Affordability:Duplex: Financing a duplex might be more challenging, but the rental income can assist with affordability.Single-Family Home: Single-family homes might be more accessible for first-time buyers, but you won't have rental income to offset expenses unless you choose to rent out a portion of the property.Property Management:Duplex: Managing a duplex involves dealing with multiple tenants and units, which can be more time-consuming than managing a single-family home.Single-Family Home: Managing a single-family home is typically simpler since there's only one tenant.Privacy:Duplex: Living in a duplex means you'll share a building with tenants, which could impact your privacy.Single-Family Home: Offers more privacy as you won't be sharing the property with renters.Market Conditions:Duplex: In some markets, duplexes may offer better appreciation potential and cash flow due to the rental income.Single-Family Home: Depending on the location, single-family homes may have better long-term appreciation potential.Long-Term Plans:Duplex: If your goal is to accumulate rental properties, starting with a duplex can be a good way to get into real estate investing.Single-Family Home: If you prioritize a more traditional living arrangement and don't want to manage rental units, a single-family home might be a better fit.

HELOC is just a line of credit like a form of credit card that allows you to tap into your equity at your convenience and the consumer can always payoff the line if they wish to get the full line amount.

Abating the odor (tobacco and Marijuana) is costly and time consuming. 

This is why the property has been on Zillow forever and hadn't been rented.

They have a place they could potentially close on by the end of the year, but its new construction and the closing is subject to change based on the builder (and the area was just in the path of Beryl, so that timeline could have been impacted), so if that's the only thing they're thinking of exchanging into, I'm inclined to suggest they consider consuming the losses now for simplicity's sake, especially if the exchange timeline can't be guaranteed to work out.

Food for thought, I can go on forever but this is the mindset I would have if I was in your shoes.

it seems like a confluence of factors have made it difficult to get started - there is lots of competition for deals, both on and off market; money is expensive; the trades are booked up forever; etc. 

Quote from @Ana Vhan: You can use it forever.

I got lots of "I'm working on it" "trying to catch up" or the forever promise of, “I’ll have it to you next week.”In the end they all backed out for one reason or another.

Unfortunately, unreliable sales people and gullible consumers are the norm.