Build a Townhouse village

I need advice regarding building a townhouse village. I have built separate houses with interiors but not villages before. I need to work out a quote for a company. How long will it take to build such a village? (as my example) There are 5 different houses.
If I may suggest: apply no textures, detail like roof tiles, gutters, outside lights

To recap, can you tell me the following:

1. PC specs needed
2. How to keep polly's low, not to choke my pc
3. How many weeks will this take on average?

I trust you can advise me or refer me to someone.

Kind regards You sent sample of village You sent