I bought a 10-unit (all 1 bed/1 bath) for 290k back in July. I had to put 25% down for the commercial loan (4.5% IR) and with closing costs came out to about 77k. I set aside 7k more for planned upgrades which included painting exterior and removing bushes out front and a few box elder trees and deferred maintenance that I knew existed. I was able to fill a few vacancies and raise the rents of the remaining tenants to increase avg. rents from $420/mo to $550/mo within 3 months. As I was able to do this 9 months sooner than anticipated, I ended up getting new windows as well for 14k. Since the deferred maintenance costed less than anticipated, I used part of the allotted 7k and the increase in cash flow to pay for the windows without investing more of my own money into the property. Along the way I also was able to get free insulation installed (~10k value) using the local utility energy efficiency initiatives as well as laid plastic sheeting in the bare crawl spaces to help with moisture and bring it up to code.
All in I have 84k invested in the 290k property, or 29% of the purchase price. I also had 10k set aside as a reserve that I did not need to touch. Through the first 6 months at the end of 2020, I'll have netted 5k or 6% of my money invested. Going forward, I'll net 20k (24% cash on cash return) each year conservatively and can still bring 7 units to market rate (625/mo).
Based on what you're trying to get for a 12 unit, you're likely in a market that will not cash flow as well. With that being said, I hope some of the percentages I shared and the actions I took can help you strategize on this deal.