If the lease is for far below market rate, this is probably an exception as the lease is not a bona fide lease. 

I agree with Will except I don't find the management that intensive. 

Then quit your job once that income is equal to or greater than your day job.You can likely do 2 deals your first year and you should always clear at least $20k on a small value flip, otherwise it is not worth the time, effort or risk, with the exception of doing worse than that on your first deal or two but gain experience and real world education (which holds its own value over actual monetary profits).

Again, that's a general rule of thumb and there are certainly exceptions, which of course is what all investors are searching for.

Use that for your base and then adjust a tad lower and you will gain more bookings because STR renters rely heavily on price in most circumstances, all else equal.

So how do you experienced people suggest I go about buying these expensive houses except waiting for years to get to that 250k downpayement savings?

My personal experience is to avoid working with friends and family in most business circumstances, real estate or otherwise. 

@Moses Lin your best bet is to speak with the lender(s) specifically, but in most circumstances, you will need landlord experience in order to count the income towards your purchasing power.

-Refinance Loan Amount, most places will traditionally refinance between 70% to 80% of the market (ARV), again their are exceptions but I would confirm this as it'll greatly impact the amount of rest of the numbers.

If you go to a regular bank that will matter greatly to them except if you use a cash rich partner.