The current monthly payments from all units will remain constant for 35 years, but obviously the value of those payments will be worth far less 35 years from now due to inflation.

So if your parents paid $40,000 for the property and today it's worth $500,000....your basis "value" in the property will be their 40,000. 

Using 50% rule (expenses excluding P&i is 50% of rent) here are the numbers;1800 (rent) - $900 (expenses) - 1468 (heloc) = negative $568/monthAt your rent point with that size unit, your expenses will ve less than depicted by the 50% rule, so let’s use a likely more accurate 40%1800 - 720 (expenses) - 1468 = negative $388/monthNow let’s imagine you self manage and you time is not worth anything (I strongly recommend believing your time is worth less or worth less than a quality PM would charge) with 8% further reduction so expenses are down to 32%1800 - 576 (expenses) - 1468 = negative $244/month. 

The payoff is worth it in the long run with reliable, on-time rent payments and tenants who are more likely to stay long-term, and take care of your property. 

If loan balance is $300k and it's worth $400k and an equity partner puts $40k to bring it current then they have about 40% of equity in the property - now they would not take straight $40k as probably more costs involved.

It may be worth letting them know about the prequalification requirements (credit score over xxx, salary above xx,ooo/year, etc.) in advance to weed people out.

Those hold about $250k worth of equity.

Cash Reserves & Emergency Fund✅ Have 3-6 months’ worth of expenses (mortgage, insurance, taxes, and maintenance) saved.✅ Keep an emergency fund for unexpected repairs and vacancies.2.

Because this is your first rental property, I would recommend finding an amazing PM company and paying them what they are worth.

Offer a personal guarantee (reduces investor risk if you have the balance sheet for a PG to be worth anything).