Yeah if the property is 100% occupied, what I'd do and what we do personally, is schedule out the leases in an excel spreadsheet with their start and end dates. Map out when the units are coming due and when you'll renovate them. Use this to come up with a renovation schedule and you can add some formulas to get an idea of what your income will be like during those times as well. It's kind of tough to explain, but if you'd like an example of what we do I'm happy to show you as well. The renovations will really affect the income the first couple years so it's important to get a good handle on how they will really affect the numbers.
If you can move tenants into renovated units, that's great IMO. We try to do this if possible, but I wouldn't bank on it. When we schedule out the renovations, we usually assume the unit will be down for two months - one month to renovate and one month to get it leased up. We feel like this is relatively conservative and also if we exceed this, we'll hit higher returns for our investors.