If it is possible not only will you get the added income stream but it will increase the value of your property tremendously.

Since the new change in Wa law makes late fees practically unenforceable, can I write in my lease that if rent is late a certain number of times then rent will increase 10%, instead of having a late fee?

If you've raised the other rents, and the market supports it, let them know rent will be increasing to the market rate - and in return, they will receive new flooring and paint.

In other words, if I took proceeds from both sales (400k on principal residence, and 250k from investment property), and purchase a new home (for myself) for 650k, will I be expected to pay capital gains on the value increase from my investment property (bought for 150k, now valued at 250k)?

So I’m sorta in a dilemma I’m currently under contract for my fourth rental and I was planning to take out another loan from my 401k to put as a 20% down payment which is around 38k but I currently got news that this company that I had applied for 3 months ago are interested in interviewing me and perhaps offering me a job which would increase my income and will have better benefits for me and it’s an overall better company for me long term than my employer that I am working with now.

That's a LOT of lost income.A general theory is a 10% or greater increase is basically a 'get out' signal.  

Purchase price: $400,000 Cash invested: $200,000 Currently renting to family and later this year will be on the open market for rent and should increase the monthly cashflow to $350.

Now, there are a handful of lenders who offer lower rates, but again, be mindful there is something within that loan to offset the lower rate such as increased points, lower leverage, draw process dictation, as-is caps, and so on..Try to refrain from “shopping” after your first deal.

If the property doesn't cashflow as is, that amount needs to be increased to cover operations and debt until the property becomes self reliant. 

@Leah ShankerI'd have to read the CC&R's and bylaws of the HOA before saying what is paid for in the event of such a calamity like flooding.Like any other business, the increased cost of doing business is always passed to the consumer.