Need help analyzing 4plex

[Dustin Battas]

Hello, I am new to investing but have been reading BP daily and listening to podcasts. I am in search of a 4plex and have tracked a few that have sold the last two months. I am currently interested in a 4plex and want to keep any feedback anyone can offer on the deal. The 4 plex was built in 1993 and is listed for $239,000. It has four 2 bedroom 1 bath units and each unit collects $525 per month on rent. The tenants pay their own utilities, garbage and water. Rent includes covered parking and a storage area for each unit in the basement. 

Monthly income from rent: $2,100

Mortgage payment (20% down), taxes and insurance $1,210

Vacancies 10%: $210 per month

Management fee 10% $210

Total Expenses $1,630

Net operating income: $470 per month

A few things I would love feedback on: What am I missing in my analysis (how much % to put aside for repairs each month etc.)? This property seems overpriced to me but what number would make it a great deal? For rent to be 10% of purchase price (10% rule) I would need to get it for $210,000. To meet the 50% rule I would need to get it much lower. What types of questions should I be thinking of here as I analyze this deal to try to learn more about the process of buying a 4plex. Thank you in advance!