A friend of mine in Austin once negotiated a partial buy back option when the seller realized they might want back in if the market soared.. from what I read in Bloomberg, that approach can work well if both sides trust each other.If the tenants’ rent covers your carrying costs, that’s a nice cushion, but you still need to clarify that buy back clause.

Or maybe the units aren't equal and one rents for $2800 covering most of the cost of living there. 

You have to walk these properties, understand where the hidden costs are outside of the spreadsheets, and understand the geographic appreciation trend and migration and population as well, none of which will be in the questions you are asking. 

There is a company names Hemlane that offers that "light PM" service that may be interesting for you instead of a full blow PM company that may cost 7-10% of revenues.

The market is slow currently and you need to check flood zones and assess insurance costs when underwriting a deal.

I’m not from the US and currently live in Europe most of the time.I’ve found some apartments that could work well for my needs—I plan to rent them out on Airbnb and reserve a few nights for myself when I travel there for work.My question is: apart from the purchase price (I’ve seen listings on Zillow averaging around $150k in areas like downtown Dallas, Old East, and Plano), what other costs should I expect—both during the acquisition and in monthly payments?

One your loans will be a higher interest rate, next you will have annual filings, the cost of a registered agent every year, and items like that. 

Do you need to increase rents in the next year to cover your costs?

One thing to consider is whether a two-family twproperty might provide better cash flow than a condo, especially with NYC’s high costs.

The IRS views it as taxable income because it’s not being used for the purpose of deferring taxes under the 1031 rules.For example, if you sell a property and only use part of the proceeds for the next investment, the leftover amount (after paying transaction costs, etc.) is taxed.