When the Fed increases rates to 6%, cold water will be thrown on this hot market.

What about a hot tub?

If you have access to tons of capital, then maybe that works for you, but I carefully employ my limited capital in the most incredible deals I can find (none less than 30% CoC so far in STRs). 

We are still very hot here in California. 

Someone else who gets involved in subleasing could probably answer better on that but many cases I have seen of it involve someone doing it behind the landlords back, and seller financing will often be the result of the seller getting the buyer to pay significantly more than a property is worth (especially in this hot of a sellers market, every instance I have seen of a seller soliciting seller financing was with a property that was $100k overpriced), unless you find a property owner who just takes kindly to you and doesn't mind giving you a start with it I would definitely recommend getting a third party BPO or Appraisal before you sign any agreement with a seller on seller financing. 

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But I also need to add other expenses on top of the mortgage like the fee of the rental management company, insurance, tax, vacancy factor, so all in all it comes with negative cash flow, and seeing negative cash flow I started rejecting the property upfront, which I think probably a not good idea considering the current market and those areas where real estate is hot.

It was definitely challenging during the pandemic with price increases/long delays for materials but the hot housing market sure made it all worth it.  

The market in this area (and likely most of Houston) seems extremely hot with most houses renting out for only ~0.6% of their value.

Get yourself a good housekeeping crew and handymen and contractors lined up for HVAC, plumbing, electrical, hot tub, and appliance.