Building multi-family unit in San Antonio,

I have come across a unique opportunity.  I reached out about a lot for sale and I wanted to build a triplex.  The lot is only 4040 sq ft which is pretty small but it's in a hot spot of town that is near all of the bars and restaurants and a group of investors are building across the street a townhouse facility.  This area is great now but even up and coming.  The seller of the lot owns the lot next to it and he approached me about doing a partnership.  Here are the two scenarios

1) I buy the one lot for 100k and build a triplex for about 250k which would be a total of 350k.  Each unit would be 2 BR 1 BA and rent for between $1300 and $1500.  The cash flow would be about $13,000 per year the first few years as everything is brand new and there shouldn't be too much in repairs but I designated $2,000 towards repairs. 

2) The buyer basically owns the land out right.  He owns one fully and owes a little on the other lot.  We would rezone the two and build an 8 or 9 unit apartment complex.  The unit would either have six 1 BR 1 BA units and two 2 BR 1 BA units or just nine 1 BR 1BA units.  I rent about a mile away and I pay 1300/month for a 780 sq ft 1 BR 1 BA apartment.  I am trying to do a cash flow analysis but I'm not sure how much to designate to insurance.  So it's hard for me to do a cash flow.  I'm not sure if it's a lot more expensive for commercial apartments.  Also, I'm not sure if they are taxed differently with regards to property taxes.  If anyone has built or owned a commercial apartment complex, feel free to chime in and give your thoughts and opinions.