@Timothy Lou it’s very hard to provide a ballpark without the specifics. Also, this really depends on the management company you hire. Do they offer dynamic pricing that maximizes your profits or will they just accept most bookings as they come to keep calendars filled. Here are my suggestions:
1. Call that reputable management company and ask them to send you comps for the area you want to buy. They should be able to tell you how much on average your future property will make. Then you can run your numbers
2. It will be more upfront work than LTR but, if you hire full house management, they can help do 90% of the work and still make your numbers work
3. Checkout my profile to see an article I posted on how to vet STR management companies, what questions to ask, etc to make sure you go with someone who knows what's they're doing
4. A well established full house management will do at least the following: guest communication, house inspections to check cleaning and that nothing is missing, claim support IF there are issues, guest screening and "party prevention", restocking of supplies, coordination for maintenance, safety and security of the house, work with you on city regulations, dynamic pricing, manage the listing online, cleaning management, monthly reports there is a lot ... but there are great STR management companies out there providing a ton of value.