I would have to say that the idea of building a £2m+ portfolio with none of your own money sounds great.
A few things to mull over:
1. To do no money down requires you to buy extremely cheap and (generally) remortgage.
2. Every time your remortage, your monthly mortgage spend goes up and as a result your yield goes down.
3. Ideally you need a rising market in which to sustain this.
4. You need very good starting yields.
5. This is the killer - your long term costs. You need sufficient capital growth to remortage on a periodic basis to generate sufficient cash flow for major works. Eg, if you have a £2m portfolio with 20 houses, you need to factor in 20 new boilers every 10 years, 20 redecorations every 3-5 years, a new kitchen in 20 houses every 5-10 years, 20 new re-flooring every 7-10 years. However every time you remortgage you are squeezing out the options for future years.
Every 10 years at a minimum - not including renewing internal doors, windows, roofs etc.
£50,000 = 20 x Kitchens @ £2500 each (basic)
£20,000 = 20 x Redecoration @ £1000 each (very very basic)
£24,000 = 20 x Boilers @ £1200 each
£20,000 = 20 x Reflooring @ £1000 each (basic but durable)
£114,000 every 10 years.
6. A £2m portfolio sounds great but you will have NO real equity as you will have remortgaged to cover your costs. Eg, a supposed £130k value against £100k purchase price. Do you REALLY think you could re-sell at £130k?
7. finally - do you trust someone else to make the decision about this for you? I know I do not.