For multifamily, leverages won't be as much until you have some experience not only with 1-4 units but also 5+ units. 

Why 4 units in 4 years?

As for valuation, I see no reasons why a Junior ADU would negatively impact additional housing unit.

Targeting single family/duplex/triplex/quadplex with 3 beds and 2 baths per unit, and $300K or less.

But to buy land just to add more units, for me is a pass.

@John Lasheri agree with you, you'd be surprised at how many people listen to Grant Cardone though, and decide that they're going to go buy a 100 unit with 'OPM' as their first deal and quit their job.i think buying something of that size with a few partners is a perfectly good goal. 

Living in one unit and renting out the others allows you to deduct 75% of expenses like mortgage interest, property taxes, insurance, and shared repairs as rental expenses, while the remaining 25% applies to personal use.

I'm interested in building 2-4 unit MF.

Congrats @Emily Pena - I'm also an agent (working mostly with investors), property manager and an investor myself (currently owning 26 rental units). 

Lastly, check any shared doors or gaps and add door sweeps or weatherstripping to block sound from traveling between the units.