Hi Gary,
Loads of people will have a difference of opinion on this one.
Has he already agreed to sell you it? Why don’t you split it between you? If not, people ask all different prices for their rounds i.e. 1.5 times the value, 2 times the value and even 3 times the value.
If he just wants out it may be easy on you. I would offer 2 times his monthly cut of the round and 50% off the cost of equipment. However, that is you working for two months without any income if you know what I mean.
Know doubt, you will get other opinions, but good look in your venture.
Andrew