I'm an investor and mortgage broker and have options for loans that go as low as $75,000 and down payments as low as 15%, which makes it easier to stay above $75,000.

The rules are designed to prevent related parties from engaging in exchanges that shift high basis property for low basis property, followed by a sale of the low basis property, effectively "cashing out" without recognizing gain.If you sell a property to a related party as part of a 1031 exchange, both you and the related party must hold the exchanged properties for at least two years following the exchange.

Meet with a local banker & schedule a time to talk with a mortgage broker, they'll give you at least a baseline of what kind of down payment options and rates are out there.After that, if you're still wanting to research more creative options, do some looking into seller financing (a very hot topic with good, and bad, advice out there), look into private lenders, and commercial financing options.If you're wanting to live in 1/4 of your quadplex, then conventional residential loans may in fact be your best option as you can purchase that with a fannie/freddy loan with very low down, and use up to 75% of the income from the property toward your own income. 

Achieved by buying low value residential housing and turning into high value tourist accommodation for Short Term Let (STL).

I would upgrade properties every 12-15 months as allowed by low down payment loans if my significant other wasn’t risk adverse and opposed to moving.

After 2 years you can apply for a “Rent consideration” (I think that’s what they called it) as long as you still live there and that may allow you to increase rents by more than the annual allowance (probably designed for unit that are very low rents).

Quote from @Bonnie Low: I love seeing your company's growth @Allen Duan!! 

We'll certainly want to keep the property tax basis as low as possible if we hold it.

There are limits to this as well (when someone stays the whole time and doesn't say anything while there), but if someone chooses to leave early or right away, give them their money back before they drill you with a 1-star review.

Most people that scale also choose one strategy to start with and scale in.