Firstly the right time is whenever you find the right deal
I don't know where your are looking to invest but why limit yourself to 100k-150k? whats wrong with 60k-100k? You need to make sure the rental received is enough for you to mortgage the home your planing on purchasing so it needs to be at least cash flow neutral, i much prefer cash flow positive myself.
In a perfect world you would want to do no money down at some point in time either now or through a re-mortgage some day or a further advance.
lets say you stick to minimum figures for a deal to stack up
117k OMV bought at 15% discount so £100k, with 85% LTV @ 5.89% means to do a no money down deal you need £614 Rent a month, is that actually achievable on the 100k home your planning on buying?
what I'm saying is as long as you are careful its a good time but make sure you keep your head straight because its going to be very easy to make some bad mistakes in the market.
Interested in 2/3 Bed Houses + Commercial Properties in Coventry + Nuneaton