Sounds like a solid starting point. Here's some questions I'd like answered if I were you:
1. What's the maximum amount of units you could build on 0.68 acres? Check with the municipality.
2. Are there any incentives available to build bonus units by providing a percentage of them for affordable housing? Check with the municipality.
3. How are the rental comps in the area for Studios, 1BR, 2BR, 3BR and their $/sf.
4. What are the sales comps and $/sf. for those comps
5. How small of parcels could you split that 0.68 acres into? You'll need to check with your municipality
Some additional food for thought:
Lot splits in my area take a lot of time, patience and money
You can finance the construction of an owner-occupied 2-4 units with an FHA loan for as little as 3.5% down but the requirements are kind of onerous.
If you built a triplex next door you wouldn't necessarily need to split the lot if you were looking at a build and hold scenario and you could get owner-occupied construction financing.
Doing 5 or more units on the same parcel puts you into commercial loan territory
You could however potentially split the lot and then build a four-plex next door and stay within residential loan guidelines.
Construction loans in my area typically lend 60-65% loan to cost
You may have enough equity in the house to be able to get that 65% financing without any cash out of pocket.
If you were able to split into 10th of an acre lots you could phase the build out of 6 single family homes: BBRR
Buy, Build, Refinance, Repeat
Good luck!