This is not as passive as other investing but it will help launch your portfolio so that you can continue to invest without needing to work additional jobs.

Additionally, since my parents are nearing the retirement age, I'd like to prioritize low-debt, high-cashflow deals.

Principal balance currently at 314kProperty Details: It's essentially a "2-in-1" property, with the main unit rented out for $1,900/month and an attached ADU bringing in an additional $1,200/month.

I could buy a LOT of umbrella (additional liability) insurance for $13,000.

OF COURSE the Contractor is going to say you need to tear it all out and rebuild the wall(s)  because that's the absolute easiest solution and adds additional work for him.

(if the buyer wants a more solid commitment)Once a buyer has spent money they are somewhat vested in buying the property and that gives additional negotiating power to the seller.

Additionally, his credit is not the best, and he has limited funds for a down payment.Any potential options or solutions that may be available?

Additionally, applicants can (optionally) upload tax forms and bank statements for our review.If you're looking for a website you can utilize on your own @Bruce Woodruff mentioned a couple that are popular.

@Cole DobbsIn addition, I may be able to help you and connect you with some key real estate investor players in the Houston, Texas market since I am an Investor myself that have done most of these real estate investing strategies and also an investor-broker who has helped over 400 investors like you. 

Your best route might be to buy a 2 to 4 unit property that you can live in and rent out the additional apartments.