I read somewhere here that I could advertise here asking for joint venture partners, how does that work?

It works over time, but the problem I see there is that you are consuming junk as well as having to make decisions on what is actually valuable information.There are plenty of opinions on how to do such on Bigger Pockets, but a lot of those opinions are misguided or wouldn't apply to you.You can do joint ventures with successful investors.

The gain is tax free, $250ksingle/$500k filing jointly.

Joint Ownership with a Formal Agreement: Another option is to keep the mortgage as it is but create a formal agreement where your sister-in-law is no longer financially responsible for the property.

Depending on your state, you may be able to enjoy a step up in basis upon the death of a spouse.Non-Community Property StatesIn every state but the community property states, spouses are treated as joint tenants with rights of survivorship (JTROS).

Would be called a joint venture .

Luckily, if you have lived in this home for at least two years, you can sell the property and use Section 121 to exempt up to $250K in capital gains (or $500K if you are married filing jointly). 

Flexibility in Ownership: Unlike joint tenancy, tenants in common can own different percentages.

I joined some facebook group and sometimes the members of the group offer a joint venture where the original investor has bought a property but will need my money for the renovation.

If a tenant is breaking their lease to leave, we will work with them, but we make them cover the gap period between tenants as "still their responsibility" - and we let them know we are really good to get the unit filled quickly - so it is a joint effort to save the tenant money, and to fill the unit quickly.All the best!